My partner's mono girlfriend is not ok with polyamory. Help?
One of my partners has a long-distance mono girlfriend who got brought into the poly situation against her will. They dated on and off before he met me, then he decided to be poly, and he would have dumped her if she didn't allow it, which I didn't realize until after I'd been seeing him for a few months. Understandably she struggles a lot with this and it's fairly obvious that she loves him and wishes she was the only girl in his life. He keeps saying that she's getting better and coming to terms with it, but my gut tells me otherwise. I've heard her speak to him about me very harshly (as in, "You had breakfast with HER? I thought SHE got up later than you.") and tries to control any aspect our relationship she can get away with (She told him I'm not allowed to send him dirty pictures despite the fact that he sees me naked regardless, and she won't let him take on any new partners). Now he keeps talking about marrying her and having kids with her while still seeing me/being poly. How can that possibly be a good idea? I've told him that I think he should either stop being poly and give her what she needs or end it with her before she gets hurt any more, but he claims he's committed to being poly and that she will eventually come around. "If she didn't want to try being poly she could dump me!" I'm concerned that if they did eventually get married she would either force him to stop being poly by threatening to divorce him or not let him see his kids, or that she would just resent me forever and teach their kids to hate me. I already hate feeling like "the other woman" and I certainly don't want to become a home wrecker. I do care about my partner and if I broke it off with him he'd be heartbroken, yet I don't know how to express my dislike of the situation without looking like I'm trying to break them up. He's utterly convinced that she'll pull through but I'm skeptical - at least if I were in her position I'd feel insecure and never be ok with it since he never really gave her a choice. So what should I do? :/