I think you did the right thing. This woman is volatile and your D should not be exposed to any more of this crazy train than possible. You will have to pick a quiet moment with your D to discuss that sometimes when people get divorced it takes a while for all of the feelings to settle down and that you did not want to make things worse by coming back. I don’t think she needs you to tell her that her mother”s behavior was over the top. Even at that age, I think she could see that. Of course just remind her that the entire thing had nothing to do with her. I don’t think I’d mention GF at all or any concerns for her. That might be confusing to your D and feel like side-taking.
You are doing the very best you can in an extremely difficult situation with a very volatile person. Note the number of times she mentioned your GF. She left the marriage after her own infidelity yet she is jealous that you have a relationship. Ignore the OM stuff, that was said to hurt you. People pretend all sorts of things in the early days relationships as part of mirroring. Who knows what his feelings are or what their relationship is.
Don’t beat yourself up. You have good instincts for your D. Your nutty EW just didn’t like being ignored and doesn’t like that you have emotionally moved on.
