Tabitha's sister is called

[Balonzette]

Magdalena
Theodora
Genevieve
Esther
Anneliese
Rosa
Josephine
?

Naomi
Manon

Meredith was the first name that popped into my head!

Another vote for Harriet here too! Tabitha and Harriet just sound so lovely together!

Margot.

Tabitha is such a lovely name.

Matilda was my first thought, but I knew the most wonderful woman called Annaliese so either would be lovely.

Tabitha and

Susannah
Penelope
Ottilie
Skye
Caroline
Katrina

Harriet or Imogen. Tabitha despite the ending in a is a very ungirly kind of name.

My DD was very nearly called Tabitha. Instead we named her Felicity. So I’m tickled that Felicity has been suggested a few times. Other names we liked were
Charlotte
Alice
Jemima
Olivia
Ursula
Constance

I have a Tabitha and LOVE her name! She is super girly and adorable. Her sister will be (hopefully!) Hattie, Harriet.

I love Ursula as a suggestion. Lovely.

OK, wild-card suggestion. Araminta?

Tabitha & Blythe
Tabitha & Iona
Tabitha & Cecilia

I'd be furious if my sister was Tabitha and I got lumbered with Harriet. I like Anneliese and Josephine best from your list. OP.

I love Esther.
Imogen?

I think Marnie goes gorgeous with Tabitha.

Ariadne

Tabitha is on my list, along with Genevieve and Rosemary.