Hi there.
Here are my thoughts on your list-
Cordelia-This is nice. I feel like it’s a little bit over dramatic sometimes. I prefer [name_f]Cornelia[/name_f]. It feels a little more bookish & gentle. And the nn [name_f]Nellie[/name_f]! But I like the nn [name_f]Cora[/name_f] too for [name_f]Cordelia[/name_f]. [name_f]Cordelia[/name_f] [name_f]Juno[/name_f] is kind of quirky in a good way.
Matilda-It’s nice enough. I like it some days & some days I find it clunky. I like the nn [name_f]Millie[/name_f]. [name_f]Matilda[/name_f] [name_f]Juno[/name_f] is cute.
Beatrix-[name_u]Love[/name_u] [name_f]Beatrix[/name_f]! It’s just elegant & spunky & vintage & quirky & charming. And it’s really pretty easy & well known, but not at all popular. [name_f]Beatrix[/name_f] [name_f]May[/name_f] is good. I like [name_f]Beatrix[/name_f] [name_f]Juno[/name_f] as well.
Thea-I like this. It’s simple & smart & just the right amount of sassy. It’s old fashioned but feels fresh. [name_f]Thea[/name_f] [name_f]Cordelia[/name_f] is a bit rhyme-y, I think. [name_f]Thea[/name_f] [name_f]Beatrix[/name_f] might be the best from your list.
Mabel-Another darling choice. It’s old fashioned & lovable & soft but still bubbly enough. Simple & well known, but not over done. [name_m]Even[/name_m] though I’ve actually heard it in real life twice in the past few months. [name_f]May[/name_f] just be a fluke. How about [name_f]Mabel[/name_f] [name_f]Dorothy[/name_f]?
Delphine-This is the only one from your list that I don’t like that much. [name_m]Just[/name_m] the emphasis of syllables is awkward to me if that makes sense. It’s different though, & not at all a horrible name.
Tabitha-This is cute. I used to be so so on it, but I know a little [name_f]Tabitha[/name_f] now who goes by [name_f]Tabby[/name_f], & it’s the cutest. She’s super clever, cheeky & wild & the name fits her beautifully. I think that [name_f]Tabitha[/name_f] [name_f]Juno[/name_f] would be fun.
Polly-This is sweet. Sounds childish, but in a sweet way & also works fine for an adult. Very easy & known, but not popular somehow. [name_f]Polly[/name_f] [name_f]Cordelia[/name_f] is good. I like [name_f]Polly[/name_f] [name_f]Matilda[/name_f] or [name_f]Polly[/name_f] [name_f]Beatrix[/name_f] even more.
Juno-Also good for a first name. I sometimes feel like it’s kind of nick-namey & better as a nn for [name_u]Juniper[/name_u] or [name_f]Junia[/name_f]. But it’s probably fine on its own too. [name_f]Juno[/name_f] [name_f]Cordelia[/name_f] would be gorgeous.
Dorothy-A nice solid but not popular classic. Kind of bookish & kind of glamorous at the same time. [name_f]Dorothy[/name_f] [name_f]Delphine[/name_f] doesn’t flow that well to me. How about [name_f]Dorothy[/name_f] [name_f]Mabel[/name_f]?
Here are a few more names that may be up your alley:
Audrey
Althea
Coraline
Clementine
Clover
Daphne
Delia
Dahlia
Dorothea
Eloise
Esme
Frances
Fern
Flora
Freya
Georgia
Georgiana
Georgina
Gwendolen
Gwyneth
Harriet
Imogen
Indigo
Juliet
Lucille
Louisa
Marian
Magnolia
Maple
Olive
Penelope
Rosalie
Ruby
Theodora
Violet
Willa
Wilhelmina
Hope this helps. 
