Very interesting post! I can't say I have any definitive answers, because I've never been in this situation. Here are some thoughts for you to considers.
- Do what Zaak says, get out there, sarge, get things going with other women. This has got to be your number one tactic, just for your own mental health. You want to be in charge of the situation, not have the situation rule your life. You can get great sex from other women too... remember it's mostly about how sexually charged up YOU can get the woman, so it's not like you won't have great sex again if you don't see this girl for a while.
- She's mixed up in her own mind about what she wants. She's willing to f*ck with your mind and heart in a rather callous way, frankly... this doesn't mean she's cruel, it just means she's way too into herself and not enough into helping/caring about other people. Is this really the kind of girl you want in your life?
Here what I would do (and I emphasize "I", because you have to really make your own choice on this one). When she wants to get together with you next time, refuse to meet her at your place or any place private. Meet her at a coffee shop or something. And then straight off tell her you don't like being screwed with mentally and emotionally, and that she can't see you again, for sex or for anything else, until she's made a decision. Tell her FLAT OUT that she can only be with you if she is willing to be monogamous with you and serious about the relationship, and that you damn well want her to start being more caring and generous towards you.
This will shock the living sh*t out of her, and she may well get mad (she'll probably say something like "You have no right to expect that of me," etc., etc.) You can tell her "I don't expect anything. I'm TELLING you what YOU have to do to be with me... take it or leave it". This is harsh stuff, but it will leave an INDELIBLE mark on her mind and heart... you are strong enough to be without her, you know exactly what you want (and you imply that you DO want her, despite not letting her near right now) and you are giving her the chance to make things good by telling her EXACTLY what she needs to do. This is being dominant, and women LOVE it, even if they initially complain.
If you act this way towards her, all of a sudden she will be unable to be with her other boyfriend without comparing him to you, in a negative way. Stay off the phone with her, no texting for at least several weeks while you are out sarging and hopefully sleeping (with a condom!) with other women. She will probably text you stuff, ignore it, even if it's "I'm thinking of you... I want to be with you..." stuff. Ignore it totally, live your life, have fun with other girls.
After a couple of weeks, you can text her that you'd be up for getting together for something casual, just for old times sake. Like visiting an art gallery, or getting a beer, or (better) taking a walk in a nice part or area of town, maybe stopping in for a coffee somewhere. Then you can lay things out for her again... you still like her and want her in your life (IF you do, after meeting other women), and in a friendly but clear manner tell her what your standards are for a possible relationship. And I do mean TELL, don't ask, ever. If she still gives you the "Well, I really love/like/respect blah blah my BF" line, you should dump her on the spot, forever... she's still too mixed up. Otherwise, you can let her back into your life, f*cking her better than she's ever had it, but only after she's made a serious promise to dump the other guy (including taking down FB pictures with him, publicly displaying/saying she's with you, never seeing the other guy again, etc.)
Make these red lines (ie. things she'd better do if she wants to keep the relationship) and keep her honest, without being jealous or micro-managing. Just assert domination and expect that she will comply.
Ok, this is my take... it's radical, but I haven't got the time or patience anymore (I'm 44) to put up with bullsh*t. AND, I know women LOVE FRICKIN' LOVE dominant men, and will often dump AFCs for them in a heartbeat, if they are TOLD to do so (yes, they want to be TOLD).
But as my sig says, take all this with a grain of salt... you have to live according to your own heart. Just be sure to keep us posted on how things go, and have fun!
Cheers, ~50