AITA?

There’s someone in my life that I (33f) have been friends with for decades. Grew up with her family and such. We are the same age. She’s been married since she was 21 and has 2 kids. We are not best friends by any means but over the last few years have kept in contact. For the last 3 years she has been cheating on her husband with some dead beat guy who isn’t serious about her, and that’s her prerogative. I’ve already told her I disagree with it and have attempted to give her advice. She doesn’t listen and literally lets this guy walk all over her again and again while she makes up excuses. I asked her kindly but firmly about 6 months ago to stop talking to me about it as I was burned out/seek therapy. She originally agreed but has since slowly started talking to me about him again and now it’s all she calls me about. I don’t even feel that we are friends anymore and that I’m just a dumping ground for her drama because I’m the only person that will listen to her.
AITA for wanting to cut her off AND tell her husband? I was friends with her first, not her husband, but I feel like I would want someone to tell me. I also just can’t deal with it anymore, she needs to talk to a therapist about this stuff, not me.
I want to tell her that she has to stop talking to me about it or cut her off, and if that doesn’t work I’m thinking of telling her husband. Thoughts? Should I have cut her off long ago?