If they are your favorites, don’t second guess them. Unless you get board of them or they don’t feel right, don’t let people change your opinions.
My favorites: Amelie, Sylvie, Elsie (I find it a bit nicknamey but can’t find a full name I like so…), Gemma, Georgia, Sophie, & Millie (my favorite from your list).
Not necessarily like, but not too nicknamey: Aimee, Maisie, Emma, Isla, Holly, Lily, Mia, Ruby, Freya, Violet, Ella & Ava
Too nicknamey for me: Lottie, Daisy, Rosie(Just to cutesy on its own), Gracie (I think it could work on its own, but I really prefer it as a nickname), Posy, & Poppy (I love Poppy as a nickname, I can’t really see it as a first name)
A lot of names like Emma and Mia are too cutesy for me, but since they are widely accepted as full names, they would be usable. Don’t let popularity bother you. One of my favorite names is Zoe, and everyone tells me how popular it is or how cutesy it is, but in reality, not so many babies are being born with top 1000 names anymore. And cutesy is a matter of taste.
That seems like a silly thing to say, honestly - there is no reason why [name_f]Millie[/name_f] or [name_f]Elsie[/name_f] CAN’T be full names. I know a [name_f]Posy[/name_f], and her parents gave her a full name… oh right, it’s [name_f]Posy[/name_f].
Their origins are from longer names, yes, but so are the likes of [name_f]Isabel[/name_f] and [name_f]Katherine[/name_f] and [name_f]Alice[/name_f]. Almost every single name in usage today is an adaptation of something else, because the flexible nature of language allows names to change over time.
The notions of ‘cute’ and ‘mature’ come from your own perception of [name_f]Millie[/name_f] vs [name_f]Millicent[/name_f], and because you seem to favour one and not the other just emphasizes your own prejudices, and saying nothing about the names themselves.
I agree that it’s key to remember that a child will grow up and have to live with a name forever. I think having some flexibility and formality is nice, a name that fits well in any situation you have to be wearing a suit. I wouldn’t go to court to stand up against injustice wearing flip-flops and pajamas, and I wouldn’t want to bring a name like [name_f]Pixie[/name_f] either—sometimes you need the full force of appearance on your side.
That’s one of the wonderful things about nicknames. You can call her [name_f]Daisy[/name_f] and name her [name_f]Margaret[/name_f], and when she needs it (or wants to branch out) [name_f]Margaret[/name_f] and its other nicknames are available.
These are too childish for me as anything other than nicknames:
[name_f]Millie[/name_f]
[name_f]Rosie[/name_f]
[name_f]Elsie[/name_f]
[name_f]Gracie[/name_f]
[name_f]Lottie[/name_f]
[name_f]Maisie[/name_f]
[name_f]Posy[/name_f]
[name_f]Daisy[/name_f]
[name_f]Poppy[/name_f]
These are cute and seem a bit diminutive, but they’re full names and still wearable on an adult:
[name_f]Mia[/name_f]
[name_f]Gemma[/name_f]
[name_u]Ruby[/name_u]
[name_f]Holly[/name_f]
These aren’t childish to me at all:
[name_f]Lily[/name_f]
[name_f]Emma[/name_f]
[name_f]Ella[/name_f]
[name_f]Georgia[/name_f]
[name_f]Freya[/name_f]
[name_f]Violet[/name_f]
[name_f]Isla[/name_f]
[name_f]Sophie[/name_f] - these last are the [name_m]French[/name_m] versions, not nicknames
[name_f]Amelie[/name_f]
[name_f]Aimee[/name_f]
[name_f]Sylvie[/name_f]
[name_f]Millie[/name_f]- Very sweet. I prefer it as a nickname.
[name_f]Rosie[/name_f]- I don’t like [name_f]Rosie[/name_f] at all. [name_f]Rose[/name_f] is so much better.
[name_f]Sophie[/name_f]- It’s adorable.
[name_f]Mia[/name_f]- I like it.
[name_f]Poppy[/name_f]- I really like [name_f]Poppy[/name_f], but I’m not sure I’d be bold enough to use it. 
[name_f]Ella[/name_f]- I’ve always loved [name_f]Ella[/name_f]. It’s a shame it’s getting so popular.
[name_f]Gemma[/name_f]- Excellent.
[name_f]Georgia[/name_f]- It’s very sweet and southern sounding.
[name_f]Ava[/name_f]- I love [name_f]Ava[/name_f].
[name_f]Elsie[/name_f]- I like [name_f]Elsie[/name_f] a lot. [name_f]Elsa[/name_f], no. It’s very harsh. I also thinks it’s an unexpected name for [name_f]Elisabeth[/name_f].
[name_f]Daisy[/name_f]- I like this strictly as a nickname.
[name_u]Ruby[/name_u]- It’s very sweet and ages well, I think.
[name_f]Freya[/name_f]- This name is very different from your other choices. [name_f]Freya[/name_f] is pretty and reminds me of snow and ice and frost, haha.
[name_f]Violet[/name_f]- I adore [name_f]Violet[/name_f].
[name_f]Isla[/name_f]- So beachy.
[name_f]Holly[/name_f]- This name has always sounded middle-aged to me, for whatever reason.
[name_f]Lily[/name_f]- I love it.
[name_f]Gracie[/name_f]- I like this only as a nickname for [name_f]Grace[/name_f]. It doesn’t seem substantial enough as a stand alone first name.
[name_f]Lottie[/name_f]- One of my favorite nicknames for [name_f]Charlotte[/name_f]! As a full name: no.
[name_f]Emma[/name_f]- [name_f]Lovely[/name_f].
[name_f]Aimee[/name_f]- I prefer the [name_f]Amy[/name_f] spelling.
[name_f]Maisie[/name_f]- Awesome. I think this stands alone.
[name_f]Posy[/name_f]- I love [name_f]Posy[/name_f], but only as nickname for [name_f]Josephine[/name_f]. It’s a shame you don’t like it.
[name_f]Amelie[/name_f]- I think it’s too cumbersome, pronunciation wise.
[name_f]Sylvie[/name_f]- So much better than [name_f]Sylvia[/name_f].
I don’t think your names are too cute. They are very nice!
[name_f]Sophie[/name_f], [name_f]Mia[/name_f], [name_f]Ella[/name_f], [name_f]Ava[/name_f], [name_f]Daisy[/name_f], [name_u]Ruby[/name_u], [name_f]Violet[/name_f], [name_f]Isla[/name_f], [name_f]Lily[/name_f], [name_f]Gracie[/name_f], and [name_f]Emma[/name_f] are my favorites.
Sorry - got caught up and forgot to answer! Anyway, my favourites in bold…
[name_f]Millie[/name_f] - This is pretty.
[name_f]Rosie[/name_f] - so lovely
[name_f]Sophie[/name_f] - eh, I prefer [name_f]Sophia[/name_f]/[name_f]Sofia[/name_f] or even just [name_f]Fia[/name_f].
[name_f]Mia[/name_f] - eh, it’s alright. I have a negative association or two for this.
[name_f]Poppy[/name_f] - I’ve never liked this. I see no appeal. I [name_f]LOVE[/name_f] [name_f]Pippa[/name_f] though.
[name_f]Ella[/name_f] - I see the appeal, but it’s slightly bland imo.
[name_f]Gemma[/name_f] - Oh, [name_f]Gemma[/name_f]. You’re probably aware that it’s dated in the UK, but I have to admit I’ve sort of started liking it since being on Nameberry. It’s like lovely old [name_f]Emma[/name_f], but also shiny and pretty like a gem. I like it.
[name_f]Georgia[/name_f] - this is my little sister’s name. I remember being shocked that it’s not popular at all outside the UK… it seems so plain to me haha. But I really do like it.
[name_f]Ava[/name_f] - I love the old-Hollywood feel, and it’s pretty but I prefer [name_f]Eva[/name_f].
[name_f]Elsie[/name_f] - it’s okay. Again, I have a very strong association with one child, so I don’t love it.
[name_f]Daisy[/name_f] - probably one of my first few favourites, and my love has been reformed in the past few years because of The Great [name_m]Gatsby[/name_m].
[name_u]Ruby[/name_u] - Eh, it’s alright. I like the Kaiserchief’s song, and it’s pretty.
[name_f]Freya[/name_f] - I like this a lot. I only have one association of a girl I baby sit for, and although it’s a good one it puts me off from ever REALLY loving it.
[name_f]Violet[/name_f] - love this.
[name_f]Isla[/name_f] - Never really liked this at all. [name_f]Iris[/name_f] is beautiful though, and I met an [name_f]Ayla[/name_f] recently which I like.
[name_f]Holly[/name_f] - a bit dated, I don’t see the appeal.
[name_f]Lily[/name_f] - So pretty.
[name_f]Gracie[/name_f] - this is my dog’s name! She’s named after the character in a [name_u]Michael[/name_u] Morpurgo book I read when I was little (I think it’s called Why The [name_m]Wales[/name_m] Came).
[name_f]Lottie[/name_f] - I like this, but it’s one of the few I can only see with [name_f]Charlotte[/name_f] (I prefer [name_f]Carlotta[/name_f] though)
[name_f]Emma[/name_f] - so beautifully classic
[name_f]Aimee[/name_f] - even though I know it’s a genuine (possibly original?) spelling, I can’t not think it looks a bit silly. [name_f]Amy[/name_f], I like, even though I find it dated.
[name_f]Maisie[/name_f] - I’m torn here - sort of nostalgic about [name_f]Maisie[/name_f] Mouse when I hear this, but I also baby sat an awful little [name_f]Maisie[/name_f] once. I prefer just [name_f]Mae[/name_f]/[name_f]May[/name_f].
[name_f]Posy[/name_f] - I really dislike [name_f]Josephine[/name_f], but [name_f]Posy[/name_f] is a very pretty stand alone name. It’s an English word for a bouquet of flowers (heard in the nursery rhyme ring-a-ring-a-roses)
[name_f]Amelie[/name_f] - makes me think of the film, so I like it. My main association, again, is another little girl I know ([name_f]Freya[/name_f]'s sister, actually!)
[name_f]Sylvie[/name_f] - [name_f]LOVE[/name_f] this, but I feel it’s a bit trendy to me, like Hipster trendy - it’ll be popular here in a year or two, I feel. It’s gorgeous though.
Sorry this was quite critical, I do like the majority of your list but because they’re all popular here some of my associations are too tied to children I know (and my mum works in childcare so I know loads of 2 year olds!) I guess it’s like being a teacher… just knowing a children with a name sort of puts me off, regardless of the association or the name itself. Your list is lovely, but they’re just not shiny and new to me so my perception is tinted.
I would suggest [name_f]Kitty[/name_f]? [name_f]Polly[/name_f]? [name_f]Edie[/name_f]? [name_f]Maggie[/name_f]? [name_f]Hebe[/name_f]? [name_f]Dora[/name_f]?
I don’t think any are ‘too’ cutesy, but I do think [name_f]Rosie[/name_f] and [name_f]Gracie[/name_f] are too nickname-y to stand alone. For [name_f]Gracie[/name_f], if you don’t like [name_f]Grace[/name_f], maybe you could use [name_f]Graciela[/name_f]? I’m sure you’ve heard all the [name_f]Rose[/name_f]- names that give you [name_f]Rosie[/name_f].
I also strongly prefer [name_f]Lottie[/name_f] as a nickname for [name_f]Charlotte[/name_f], but I saw [name_f]Charlotte[/name_f] in your signature so I presume [name_f]Lottie[/name_f] would be a nickname for [name_f]Charlotte[/name_f]?
I’m on the fence over whether [name_f]Posy[/name_f] needs a full name or not.
I love all of them, [name_f]Rosie[/name_f] and [name_f]Sophie[/name_f] are my faves.
Personally, I think they can be used as first names but I just like having 2 for 1 names, so I pick a longer form.
[name_f]Millie[/name_f] - Very nice. I like this as a nn for [name_f]Matilda[/name_f]
[name_f]Rosie[/name_f] - love, although I prefer as a nn for [name_f]Rose[/name_f]
[name_f]Sophie[/name_f] - [name_f]LOVE[/name_f], [name_f]LOVE[/name_f], [name_f]LOVE[/name_f]! One of my favorites, see my signature
[name_f]Mia[/name_f] - ok
[name_f]Poppy[/name_f] - dislike
[name_f]Ella[/name_f] - ok
[name_f]Gemma[/name_f] - strongly dislike
[name_f]Georgia[/name_f] - very nice
[name_f]Ava[/name_f] - ok
[name_f]Elsie[/name_f] - Really nice!I like this as a nn for [name_f]Elsa[/name_f].
[name_f]Daisy[/name_f] - not my favorite
[name_u]Ruby[/name_u] - eh
[name_f]Freya[/name_f]- eh
[name_f]Violet[/name_f] -eh
[name_f]Isla[/name_f] - One of my favorites!
[name_f]Holly[/name_f] - not my favorite
[name_f]Lily[/name_f] - really nice!
[name_f]Gracie[/name_f] (don’t like [name_f]Grace[/name_f]) - I love [name_f]Grace[/name_f], but I’m not a fan of [name_f]Gracie[/name_f], especially not as a full name
[name_f]Lottie[/name_f] - [name_f]Love[/name_f], especially as a nn for [name_f]Charlotte[/name_f]
[name_f]Emma[/name_f] - nice
[name_f]Aimee[/name_f] - dislike
[name_f]Maisie[/name_f] - [name_f]LOVE[/name_f]! Especially as a nn for [name_f]Margaret[/name_f] (see my signature again)
[name_f]Posy[/name_f] (not liking [name_f]Josephine[/name_f] as much) - ok
[name_f]Amelie[/name_f] - not my favorite
[name_f]Sylvie[/name_f] - like
I didn’t find anything you said too critical at all actually, you weren’t very negative 
I’m going to school to be a teacher, and one little girl I work with right now (for college I have to work in a classroom as well) is named [name_f]Eva[/name_f] - entirely turned me off of the name, haha. I know a little [name_m]Colyn[/name_m] who turned me off of that name as well (like, the name [name_m]Colin[/name_m] with a creative spelling.).
I know [name_f]Gemma[/name_f]'s dated, but I keep coming back to it, haha. I used to love the dated names from the UK though, especially ones like [name_f]Gemma[/name_f] and [name_f]Tia[/name_f].
I love [name_f]Polly[/name_f] (personal connection for me) and [name_f]Edie[/name_f] 
For me there are just a few that stick out as being too nicknamey:
[name_f]Millie[/name_f]
[name_f]Rosie[/name_f]
[name_f]Gracie[/name_f]
[name_f]Lottie[/name_f]
[name_f]Maisie[/name_f]
My favorites from your list:
[name_f]Aimee[/name_f]
[name_f]Sylvie[/name_f]
[name_f]Isla[/name_f]
[name_f]Gemma[/name_f]
[name_f]Elsie[/name_f], [name_f]Lottie[/name_f], and [name_f]Posey[/name_f], but I really like them all. What are the middle names, this really set each name apart and gives a vibe that your going with. It sounds like you prefer short and sweet names. If you need more option are want to compare contrat check out: Dulcet Dainties - British Baby Names
I haven’t decided on middles yet, but I’m working on it I do definitely prefer them - and the British style of naming is very much how I seem to work. I love britishbabynames.com! That’s actually where I saw [name_f]Posy[/name_f] :') I have most of those names on my long list, they’re wonderful (much like [name_f]Elea[/name_f] is for compiling the lists!)
[name_f]Georgia[/name_f], [name_f]Violet[/name_f] & [name_f]Freya[/name_f] stick out to me as being more sophisticated if that’s what you’re looking for.
[name_f]Millie[/name_f] - sweet, but I do feel as though it’s lacking.
[name_f]Rosie[/name_f] - very cute! Not a full name, but a wonderful nn. Her full name could be [name_f]Rose[/name_f] though, that would be fine!
[name_f]Sophie[/name_f] - Very nice! [name_f]Sophie[/name_f] is a name with history, and has been popular for a long time! I like it more than [name_f]Sophia[/name_f] and other variations.
[name_f]Mia[/name_f] - It’s ok, but I knew a [name_f]Mia[/name_f] when I was young and she was awful, so my judgement is clouded.
[name_f]Poppy[/name_f] - I like [name_f]Poppy[/name_f]. It’s sweet.
[name_f]Ella[/name_f] - A name nameberry portrays as popular, but isn’t actually that popular/common. A very nice name!
[name_f]Gemma[/name_f] - NMS, but i don’t dislike it.
[name_f]Georgia[/name_f] - Very sweet. Has a southern, common feel to it. Very approachable, but daring.
[name_f]Ava[/name_f] - NMS. I don’t understand the appeal of [name_f]Ava[/name_f], but I’ve known 3 and didn’t really like any of them.
[name_f]Elsie[/name_f] - Too much of a nickname. [name_m]How[/name_m] about [name_f]Eloise[/name_f] nn [name_f]Elsie[/name_f]?
[name_f]Daisy[/name_f] - [name_f]Love[/name_f] [name_f]Daisy[/name_f]! I’ve always had a soft spot for flower names, Dizzy Daze [name_f]Daisy[/name_f].
[name_u]Ruby[/name_u] - don’t love the jemstone names half as much as flower names.
[name_f]Freya[/name_f] - [name_m]How[/name_m] is this suddenly so nameberry popular? I don’t love it.
[name_f]Violet[/name_f] - So wonderful! GO flowers go!
[name_f]Isla[/name_f] - Approachable, unique and kind, [name_f]Isla[/name_f] is fit for a princess or a tomboy!
[name_f]Holly[/name_f] - Sweet.
[name_f]Lily[/name_f] - Maybe one of my less favourite flower names because of it’s popularity.
[name_f]Gracie[/name_f] (don’t like [name_f]Grace[/name_f]) - Her legal name would have to be [name_f]Grace[/name_f]. and you could call her [name_f]Gracie[/name_f].
[name_f]Lottie[/name_f] - This is a nickname to me. A wonderful nickname though!
[name_f]Emma[/name_f] - too gentle. Not enough pizzaz!
[name_f]Aimee[/name_f] - [name_m]How[/name_m] do you pronounce this?
[name_f]Maisie[/name_f] - Loving [name_f]Maisie[/name_f] atm!
[name_f]Posy[/name_f] (not liking [name_f]Josephine[/name_f] as much) - You’re certainly a nickname sort of gal!
[name_f]Amelie[/name_f] - Wonderful! Very french!
[name_f]Sylvie[/name_f] - Sweet. Unexpected, yet well known! [name_f]Sylvie[/name_f] is a wonderful name!
People are calling them cutesy because they are, however, there’s nothing wrong with that! I wouldn’t call [name_f]Mia[/name_f], [name_f]Sophie[/name_f], [name_f]Ava[/name_f], [name_f]Georgia[/name_f], [name_f]Gemma[/name_f], [name_f]Freya[/name_f], [name_f]Violet[/name_f], [name_f]Emma[/name_f], [name_f]Amelie[/name_f], or [name_f]Sylvie[/name_f] cutesy. And if some of the popularity doesn’t bother you, then that’s fine! Overused, [name_f]IMO[/name_f], isn’'t really a thing. It just means continuously popular.
I love almost all your names! I too love the nickname-y names! But I want my future kids to be able to have a nickname (because I don’t), so I’ll give them a proper full name and a nickname.