First my above post should say she is NOT alcoholic.
I hear Mako. I hate the guilt and am quite aware I do it myself. I was a limited contact with her. But, I realized in hindsight that she was gearing up to cross my boundary by again calling me every week and bringing up topics I dont want to talk about with her. Then after a few more things I knew that was it. I think part of my guilt is from deciding to finally stop putting up with her. I have done it my whole life why not keep doing it. Plus there is the guilt from knowing she is deliberately sabotaging her life to force my sisters and I to be involved.
It is just an ugly vicious cycle. Like your mother my mom is also an adult child and knowing her family as intimately as I do I understand where and how she came to be who she is. Yet I still feel somehow some of this is my fault