I wholeheartedly agree with Sally. Some people are just that - poison. And no matter how hard you try to get along with them it's all a one-sided effort. Yours.
When my MIL was dx with bone cancer several years ago I immediately contacted her to offer my help. It was just the first thing that entered my mind to do. I really didn't think it through before calling her. I was "dismissed" and told that my help wasn't needed or wanted.
To this day I still don't know what in the world her problem with me is. Unless she blames me for her son's death which is absolutely ridiculous. But in her mind (or lack thereof) it would make sense.
She started her attacks while we were planning the funeral and it never stopped after that. Lots of us were scratching our heads. I truly believe she is "out of her mind". Her thought process is not normal.
Sometimes we can only control our reaction to these folks. We can't control them but we can control ourselves and what we allow into our world. I just refuse to allow her to get to me anymore.
If she was ever in need and I was her only source of help then yes, I would definitely help her. Would she do the same. No, I seriously doubt it. But she has to live with herself and I have to live with myself. I'd rather lay my head down each night with a clear conscious.