I’m sorry that you’re going through such a difficult situation, I speak from experience…I had to make the same decision last year with my younger sister because she is very hateful towards me, I always mothered her being seven years older and I loved her very much, there’s nothing I wouldn’t have done for her. I got cancer a few years ago and initially she was sort of supportive but not really, she was more concerned how my diagnosis would affect her, I suppose it’s normal but she just didn’t care about me, I would always try to help her when she needed it but now I just don’t have the energy for her demands and drama, she accused me of not being there for her when she needed me. I read that when you’re sick you should avoid the people who don’t offer you any support or help and that they will only drain your energy that you need to help yourself, I finally did so and it was painful but I’m still working on it. I guess it’s a personal decision and each person has their own way of coping, I still have bad moments but I stand by my decision.

I recently got rid of my only sibling, a sick, toxic, mentally ill person. I'm not going into a song and dance here. She finally plucked my last nerve and the fight became nuclear, destroying everything. What's left is just some radioactive fallout that will quickly dissipate. Cue 'I'm Free' by The Who. FREE!
I made it clear in no uncertain terms that I don't ever want to see her, hear from her, hear about her ever again. Stick a fork in me because I am DONE.
I am FREE!
No you aren't nuts! Do whatever you have to to protect yourself. Draw the boundary and stick to it no matter what.
God bless.