Just wanted to say congratulations on all the positive things happening in your life and that the posters here have excellent advice. I'm sorry you are in such a tough position. I think it's important to put your health and happiness first. I know you love her and you can be there for her without her sucking you in.
As a mentally ill mother to a 17 year old daughter, I do everything in my power to minimize any repercussions for her. I give her all my love and support and really try to help her blossom and fly. I'm sorry your mother isn't able to do the same.