Which one would be your pick for a sister for [name_f]Anastasia[/name_f]? MN would most likely be [name_f]Tulip[/name_f] and suggestions are welcome!
[name_f]Isadora[/name_f] [name_f]Tulip[/name_f]
[name_f]Christiana[/name_f] [name_f]Tulip[/name_f]
[name_f]Marina[/name_f] [name_f]Tulip[/name_f]
[name_f]Seraphina[/name_f] [name_f]Tulip[/name_f]
[name_f]Cordelia[/name_f] [name_f]Tulip[/name_f]
[name_f]Celestia[/name_f] [name_f]Tulip[/name_f]
Wow! What a great list! It’s hard for me to decide, but my top 3 contenders would be [name_f]Cordelia[/name_f], [name_f]Isadora[/name_f] and [name_f]Seraphina[/name_f] (in that order). I love them paired with [name_f]Tulip[/name_f]. Well done!
My favourites with [name_f]Anastasia[/name_f] would be:
What about:
[name_f]Genevieve[/name_f]
[name_f]Ophelia[/name_f]
[name_f]Clementine[/name_f]
[name_f]Imogen[/name_f]
[name_f]Evangeline[/name_f]
[name_f]Aurelia[/name_f]
[name_f]Ottoline[/name_f]
[name_f]Calliope[/name_f]
[name_f]Persephone[/name_f]
[name_f]Emmeline[/name_f]
[name_f]Josephine[/name_f]
[name_f]Cecilia[/name_f]
[name_f]Theodora[/name_f]
[name_f]Georgiana[/name_f]
[name_f]Mirabelle[/name_f]
[name_f]Isadora[/name_f] is my favorite with [name_f]Anastasia[/name_f].
Loooove [name_f]Cordelia[/name_f]! [name_u]Ever[/name_u] since [name_f]Anne[/name_f] of [name_u]Green[/name_u] Gables lol. I think [name_f]Cordelia[/name_f] [name_f]Tulip[/name_f] is sorta cute, I’d probably choose something else but it is alright, and the name definitely goes with [name_f]Anastasia[/name_f]. I also like [name_f]Cecilia[/name_f] and [name_f]Amelie[/name_f] but that may be too similar for your liking. In my opinion sibling names can be close, I’m not sure why people don’t think so but each to their own I guess. [name_f]Orelia[/name_f] or [name_f]Aurelia[/name_f] and [name_f]Calista[/name_f] are pretty too and so is [name_f]Calliope[/name_f] but not sure how people would take the pronunciation…absolutely love the nn [name_f]Callie[/name_f] though!
I like [name_f]Christiana[/name_f], [name_f]Marina[/name_f], and [name_f]Celestia[/name_f] (though I prefer [name_f]Celeste[/name_f]). I’m not a fan of [name_f]Tulip[/name_f], but it does flow with all the names.
Vote for [name_f]Isadora[/name_f] [name_f]Tulip[/name_f]. 
My top two from your list are [name_f]Christiana[/name_f] and [name_f]Isadora[/name_f].
[name_f]Cordelia[/name_f], [name_f]Christiana[/name_f], or [name_f]Isadora[/name_f] are my votes! I also love Teadora with [name_f]Anastasia[/name_f], and Teadora [name_f]Tulip[/name_f] would be cute!
I like [name_f]Seraphina[/name_f] the most, and [name_f]Seraphina[/name_f] and [name_f]Anastasia[/name_f] are great together:)
[name_f]Celestia[/name_f], [name_f]Isadora[/name_f], and [name_f]Cordelia[/name_f] definitely