I don't know if it applies, but that is what I did. I took a stand.
I told W, after she had told me she wanted to work on M, that there could be no contact with OM. The thing I did badly was that I came across as demanding. She had stated that as a problem of mine in the past.
Part of her connection with OM involves going out with her friends every week to do karaoke, which is where she met OM. She felt like I was saying she couldn't be around her friends. I tried to reason that there were other places we could go, but she just made up excuses as to why that wasn't a workable solution. The result is she moved out.
Looking back I would have addressed it differently. I would have told her that I won't tolerate her seeing OM and at the same time I feel she is free to do as she pleases. I would have made it clear that it was her decision to make.
I feel as good as possible about where I'm at right now. I made the right decision for me. I'm living my life and enjoying myself and it appears W is doing the same. I'm not angry, mad or resentful at W and have no problem being a friend to her. I realize that I'll survive and be happy if she is with me or not. I know that this can't go on forever, that something will change. It just gets, at times, very tireing doing the limbo shuffel.
"Our life is what our thoughts make it."
Marcus Aurelius