I agree with Martian Destiny. Just because someone is your mother (insert any family member here), doesn't mean you are beholden to endure whatever **** they give you.
As a disclaimer, I will say that my relationship with my parents was good. My mom died almost 15 years ago. I miss her, but, life goes on. I talk to my dad, who lives in CA, but it's not a super close relationship. That's nothing new.
But, I do have some experience with "divorcing" a relative. I "divorced" my aunt (my mom's sister). She always has been the drama queen in my family, with some definite underlying mental health issues. When her DH died at age 52, she pretty much declared her life was over, and took it as a signal to run everyone else's life. This occurred right at the time I moved back here. I was able to be firm with boundaries, and still be with my family for holidays, etc. She was too busy trying to run her own kid's lives. When my mom got sick, she thought I was cruel and heartless for not leaving my own family and going to CA indefinitely. My mom specifically did not want me to do that! My aunt interfered with my mom's medical situation, drove my dad and brother crazy, and generally acted crazy when we ignored her.
Over the years, I tried with her, but she only wanted to tell me what to do. When one cousin became super religious and gave my DH crap about not wearing a yarmulke on Passover and I no longer could take the other cousin, who has always been a xenophobic, gun touting, right winger, I stopped calling. It's been a year and a half, and it is better. I feel badly that my kids have lost contact with the few relatives they have, but they witnessed her craziness growing up, so it's in context. Life is too short.