[quote YankeeDad]@Elan76, I completely empathise with your feeling of having been betrayed when she ended up in bed with this other guy just a few days after your breakup. It is quite possible that her desire for him was the source of the problem all along, and that she provoked the arguments with you so that she could be with him whilst avoiding feelings of guilt by giving herself a way to blame you for the relationship breakdown.
Regarding what kind of relationship you would need going forward in order to continue with her, I wonder whether it mightn’t be more effective if you express it to her in terms of your own needs, not an objective moral standard that separates the good from the bad. A lot of people may happen to share similar needs, and I am one of them, but I believe it is both more powerful and less judgemental to “own” it as one’s personal truth
If you tell her “fidelity and commitment is the right and decent way to have a relationship, and doing otherwise is the wrong way,” then she may just feel controlled and judged and put down and belittled. That is unlikely to get a good result for anyone.
If, on the other hand, if you tell her something more like “I need to be in a relationship that includes fidelity and commitment from both partners in order to feel secure and loved,” and just see what she says, that might work better. If she avoids the topic then follow up questions like “how would you feel about that?” Or more directly “Would you like to share that kind of relationship with me?” might start to elicit the information you seek.
Of course, the proof will be in the pudding, and if she says that is what she wants but then does not behave accordingly, you will need to listen to her actions, not to her words.[/quote]
Thanks so much for your response. I can see what you are saying and how my approach may come across. I will try the way you have suggested so thank you for your advice.