Schizophrenic Mother-In-Law

My husbands mother is a paranoid schizophrenic. Not on treatment bc she doesn't believe there is anything wrong with her. She says all this random bs about "thats the problem" and will say "its bc of what ive been dealing with over here" literally with no story or explanation of anything!!!! That's me explaining it briefly. Point is, I cannot stand to be around here. She makes me uncomfortable & he gets super pissed off bc he is tired of dealing with her craziness. He has for years. But when I don't want anything to do with her, he gets mad at me! And says "I never want to do anything with HIS family." He only has his single mentally sick mother. His father & his father's girlfriend. I have a HUGE family & we constantly have family parties. But bc i dont want to deal with his mother.... He wont go to MY family parties anymore. Why do I have to be the one to go to family parties without my husband EVERYTIME all bc I cannot handle being with his mother for 5mins!? His dad never wants to do anything with us bc his girlfriend has 6 daughters and he only cares about them now. MY family has welcomed him in as part of the family since day 1 & he doesn't want to go to my family parties bc he knows I hate dealing with his mother. How should I approach this conversation w/o starting an argument