No advice, but just wanted to let you know your post resonated with me because I'm in a similar situation with my sister. The anger part - gosh I relate to that.
I didn't unfriend my sister by I unfollowed her and her boyfriend and that suits me just fine. I keep communication with her to a bare minimum and my parents fortunately no longer try to repair our relationship because they're at their wits' end as well.
What has helped me a lot is the knowledge that 1) my sister's behavior is not unique and 2) as a result, I can't take it personally. I know she isn't necessarily lashing out at me, but at what I represent.
Don't get me wrong. I get angry. I get VERY angry. The difference is now that I know that the anger isn't going to get me anywhere.