It's very hard to write off friendship with your own mother as a lost cause. I've always tried hard to make the best of even very troubled relationships with family members. Looking back on that, I don't know that I really did myself any good. Deciding to "keep her away" is an option you have every right to seriously pursue. The financial thing probably was just manipulative B.S. that, unfortunately, your sister bought into. I believe these patterns tend to never change. Putting whatever distance you need to put between you and your mother may actually help you recover from your depression.