Death by 1,000 paper cuts

I am at the end of my rope with my mom. She was not physically or verbally abusive growing up (I don’t think - she said some cruel things sometimes…), but my dad was at best completely emotionally absent and treated me like a burden, at times outright mean and very occasionally physically abusive, and she took his side 100% of the time. I’m completely estranged from him at this point and feel ok about it. They divorced 20 years ago and yet it continues, and she will choose a man over her daughters every time, including her trash second husband. She shows zero effort to actually know me or my kids, only cares about appearances, etc etc. I’ve tried to explain my perspective and how she’s hurt me many times but she’s only ever defensive. This past winter I asked for some space and have been low contact for the most part, other than a quick call a few times a month and she attends most stuff for my kids. Well, she recently did something again that shows she defers to her husband over supporting me and I think I’m ready for a long term or permanent break from her. Feeling kind of guilty because it’s not like any/most of these things are that bad in isolation, just the four decades of accumulated hurt is at a tipping point. Not really sure why I’m posting this, I guess I’m interested in hearing from others who have been down this path and their experiences. If I cut her off completely I’m afraid I will feel like an orphan, even though both parents are living.