[name]Fran[/name],
My thoughts on your list, which is fabulous!
[name]Dahlia[/name] - Such a pretty name, but it feels a bit fiercer - weird word, I know - than [name]Lacey[/name] and [name]Pearl[/name], which both have a more delicate image to me. Could be because of the [name]Black[/name] [name]Dahlia[/name] connection, though…
[name]Evie[/name] - So cute! I love [name]Evie[/name] and [name]Edie[/name]. [name]Lacey[/name] and [name]Evie[/name] sound a bit similar, but they are really sweet together.
[name]Rose[/name] - My only concern is [name]Rose[/name] [name]Reeves[/name] being a bit abrupt, but otherwise it is very nice! Perfect style match.
[name]Elsa[/name] - I was about to suggest [name]Elsie[/name] up with [name]Evie[/name] and [name]Edie[/name], and then I saw [name]Elsa[/name]. So soft, delicate, and feminine, just like [name]Lacey[/name] and [name]Pearl[/name]. [name]Elsa[/name] [name]Reeves[/name] is gorgeous.
[name]Holly[/name] - Hm. Honestly, this sounds a bit dated to me, and I’m not sure I love it with [name]Lacey[/name] and [name]Pearl[/name].
[name]Phoebe[/name] - Such a spunky, fun name! I love [name]Phoebe[/name]! Would it bug you to have two P’s, though? Stuff like that usually bugs me…
[name]Ruby[/name] - [name]Lacey[/name], [name]Pearl[/name], and [name]Ruby[/name] are adorable together. [name]Ruby[/name] and [name]Pearl[/name] are both obvious gem names, though, which makes me a bit wary of this set.
[name]Ivy[/name] - I love [name]Ivy[/name]! Such a neat, classic name, and it really works with [name]Lacey[/name] and [name]Pearl[/name]. Not quite as soft, but still a great sister!
[name]Flora[/name] - Hm. You might be on to something with [name]Flora[/name] [name]Reeves[/name]. It is a bit tough to say! Aw, man! I loved it.
[name]Helen[/name] - [name]Lacey[/name], [name]Pearl[/name], and [name]Helen[/name] make a nice set, yes. To me, though, [name]Helen[/name] doesn’t have quite the personality that [name]Lacey[/name] and [name]Pearl[/name] have. It’s classic and calm, but not subtly spunky. [name]Just[/name] my opinion…
[name]Gemma[/name] - And you save the best for last! A subtle nod to a gem name without being a gem name is definitely the way to go, I think. [name]Gemma[/name] has the same modern, playful feel that [name]Lacey[/name] has, yet it feels romantic, feminine, and classic like [name]Pearl[/name]. Absolutely perfect. [name]Love[/name] it!
So, my favorites in order are [name]Gemma[/name], [name]Elsa[/name], and [name]Rose[/name]. 
[name]Lemon[/name]