My mom is so bitter and hateful sometime, what can i do?

I love my mom, she is a good person that’s been through a lot, she has chronic health problems (rheumatoid arthritis), she is stressed most of the time and lashes out so easily and quickly, she had a pretty heavy fight with my father’s family 8 years ago, and ever since we DO NOT talk to them whatsoever, the thing is, she seems so triggered by that incident till this day, i showed her a picture of my old primary school friends i found on facebook and she mentioned that one of them got married recently to a cousin of my dad, she started saying pretty bad stuff, her problem was with said cousin parents and how they didn’t take her side against my granddads, and i told her you’re taking it personally and we were never this close with these people, and that she doesn’t have to consider them her “enemies”, she lashed out on me and wished that i’d be abused like her to know how it felt😅 I get that she is traumatized, but i get the feeling that she doesn’t want to get better, to let it go and MOVE ON, she talks about this incident every chance she gets that it is sickening at this point.