girl's name that sounds a bit like...

[makescakeswhenstressed]

Annabel.

ie: it needs three syllables. Quite a middle class/upper class name. Someone you'd imagine to be slightly reserved but terribly polite.

and before I get jumped on this is for a character in a story!

The person who springs to my mind is a Francesca!

Genevieve

Christabel, as in Pankhurst.

Arrabella
Leonora
Lucinda

Rosalind

Harriet
Victoria

Victoria doesn't have 3 syllables though obvs

Clarabel

Persephone (but four syllables though).

Eugenie

Fernanda

Isabel

Cressida

Is there a reason why you can't use Annabel as that's what you're picturing for your character? What about Juliet or Beatrice. I would put Annabel, Juliet and Beatrice in the same sort of category.

What kind of book is it?

Meredith
Abigail

Josephine, Juliet.

Nathalie
Emily

How old is this person? Naming trends change.

Breathing: can't use it because I've used it before.

A rude one

and she's about 25 I guess

Jilly, is that you?

Miranda

Phillipa

Camilla

Mirabelle