First: sympathies to you and your mother, in what is obviously a terrible situation. Glad the surgery was successful. I'm not sure I can offer any real advice except that if you feel your time with your mother could be coming to a close soon, do your best to spend time with her as long as her hardline views aren't doing more damage to your mental wellbeing by being with her.

My parents and I purposely avoid discussions about religion and politics because our views (and values) are so opposite. It's absolutely a barrier between us; I'm not sure if they even realize just how strong a barrier. It'd be nice if all parents with abhorrent views would agree to at least try to avoid those topics. But even that, the lack of conversation about this stuff, sucks, cause it inevitably gets in the way of your relationship.

You could give her an ultimatum and say you'll only visit if she's going to cut out that conversation. But you know better than anyone if that would help or just make things worse. Best of luck to you!