That’s quite the list Op!
My main thing would be that Barnaby is a lovely name with a rich cultural history, and if I were his sister I’d be expect the same, so -
1sts
Cecily
Flora
Stella
Nancy
Aster
Vivienne
Allegra
Other ideas - Rosanna, Claudia, Marianne, Jemima, Tabitha, Oona, Esther, Philippa nn Pippa, Adela, Lois, Caroline, Emmeline, Iona, Isadora, Dorothea nn Dora / Dorey, Francesca, Serena, Frances, Katharine nn Kit or Kate, Susannah, Edwina, Jasmine, Genevieve, Cassia, Fernanda
2nds - nice but slightly odd w Barnaby
Elva
Frida (Freida better)
Sydney
Romilly (not odd but Too Much)
Anouk
Anouska
Robin
Xanthe
Dillon (it’s Dylon)
Evangeline - it does go with Barnaby, but she will be one of a zillion Evies
Paloma - lovely but jars with Barnaby a bit
Cosima - same, but a bit less lovely
No
Alva - ugly. Aphra?
Stevie - only if short for Stephanie, and that’s not great with Barnaby
Anaise - what?! Annelise is nice
Mabel - meh
Aurora/Rory - former is too Disney princess, latter too popular as a boys name
Fleur - always sounds like someone trying to get to the loo before throwing up
Etta - meh
Delphine - sounds like a drug store perfume
Mila - meh
Gabriella / Gigi - OTT, also will likely end up Gaby
Iris - lovely but done to death
Maeve - ugly, also overused, weirdly
Uma - ok, but very weird combo
NO!!!
Bluebell. She’s a baby, not a barbie, and one day she will be a grown woman
Clover - as above, but substitute cute baby cow for Barbie
Effie - wet as a full name, sweet as a nn for Euphemia, but that’s too much
Ever. Do you mean like the French pronunciation of Eva?! Anyway, no.
Nola - no, she isn’t 77 and the victim of a repressed Catholic childhood
Marigold/Goldie - just no:They called her Marigold and hoped she would..
Marla - no. Depressed 1970s barmaid
Marlowe - no. Very low rent indeed
Pandora - no, come on - Pandora’s box?
Primrose - wet and Prim. So no.