A sister for Alexandra should be called....

[language]

Isabelle
Sophie
Estelle
Helena
Florence
Alice

or something else?

Beatrix.

Isadora

Katherine

Both lovely Russian princess names.

absolutely nothing to do with my name being Katherine Alexandra nothing at all

I have an Alexandra. Her sister would have been Honor.

Out of your list my favourite is Helena.

I have an Alexandra and her little sister is called Elizabeth.

outs oneself they are known as Lexie and Ellie

Seraphine
Delpine
Eliza
Cecilia

Victoria. Obvs. :)

I have a Matilda and am considering Alexandra for sibling on the way!

Francesca! I know an Alexandra whose sister is Francesca. They go really well together.

Olivia, Caroline or Fancesca

I have an Alexandra and her sister is Honor.

Sophie!

Going down hill, you have excellent taste

Olivia was my first reaction

Chloe.

Silvia
Bianca
Marion

Francesca is great, but I know two who are known by the nn Frankie which turns me off it so much!

Oh Shredded, I have an Alex and Ellie

Aw, I like the nn Frankie. Reminds me of the song.

Rowan.

Susanna, nn Zanna
Thalia
Helena is lovely too but for some unknown reason peeps around here pronounce it 'Hel-eena', as if the second e was an i!
Victoria nn Tori or Toria
Your names and the suggestions are lovely!

Your whole list is lovely, but Helena is the nicest IMO. Only pronounced Helen-a though, can't stand the Hell-ay-ner version.

Charlotte.

Francesca, Victoria or Elizabeth