From the beginning of chapter 16:
"She could imagine Mrs. Clay to have said, that "now Miss Anne was come, she could not suppose herself at all wanted"; for Elizabeth was replying in a sort of whisper, "That must not be any reason, indeed. I assure you I feel it none. She is nothing to me, compared with you";"
Anne hears her own sister speak of her (Anne) like this. Elizabeth says straight out that she doesn't care about Anne, that she much rather wants the company of Mrs Clay who really is a "nobody".
That comment really hurt me on Anne's behalf. It seems really mean.