Sally is a nickname for Sarah, so it's the same person.

I, too, loved Amelia's letters. She has so much to say, but alas, only has enough paper to say that she has a lot to say! Too funny.

I wondered how Jane decided to title this "Amelia Webster?" She's not particularly the heroine of the piece, though she and her George do account for 4 out of the 7 letters...