Hi Bloopsy/Shadow, glad to hear that you are feeling better! What October said is absolutely true, we all make mistakes, but this makes us good people. The only people who feel that they never make mistakes are N's, and we all know that they make more mistakes than anyone else! Having said all this, I'm not sure that you made a mistake. You felt that you had a reason to fire your sponsor, and from what I've read about her I think you might have done the right thing. Maybe now you feel afraid for trusting your feelings and start punishing/second-guessing/devaluing your own decision? After all, in a situation like this there really is no "right" or "wrong", there is only what you feel comfortable with! You are in AA to take care of yourself, and only you can determine the "right" way to do this.
As for your sister; I don't know much about the theories of therapy, but I do know that if it was me, I would like to know. Maybe you could ask her if she has any idea why she feels so bad? And tell her about your experiences, and then maybe she will reach her own memories through yours? Just a suggestion, do what you feel is best. And take care of yourself, you are a wonderful, warm, open person who deserves care and love!