The way to detach is to slowly and steadily spend less and less time together. At your current level of "attachment" you are completely unable to withstand a "face down".
And a "face down" is:
Her: Maybe we should just break up
You: I agree
Her: (getting more aggressive) I really mean it
You: (firmly) Me too
Her: Fine then maybe I should go pack now
You: (silent) because at this point further conversation is counter productive
But you are going to need a few months of steadily cutting back on time together and if it was me, I would completely stop initiating sex. You are letting her bully you. That isn't really about her, its about you.
We have talked about it at greath length, she insists over and over that she's never going to him, that he "screwed me over", etc. They don't text/call one another, there is nothing sexual in the Facebook stuff, but yes this is a major problem. From time to time she has talked about how she's trying hard to get over him, she will delete him from Facebook, but then add him back later on. She always has some odd excuse about it too. I am not sure how deep a person can say this is in terms of an emotional affair as there is really no participation. The one incredibly WRONG thing that happened was them visiting one another.
I tried talking to her about it last night but the conversation got turned to something else, we were having a very good intimate conversation at dinner about some other issues so I didn't get it steered back to the other man, but it will, very shortly. I'm trying to work on what I'm going to say, because inevitably she first plays the ANGER card, says mean things to me, then she plays the MAYBE WE SHOULDN'T BE TOGETHER card, and finally breaks down crying with the I AM SUCH A BAD PERSON, I AM WORTHLESS card.
I do NOT know why seemingly any conversation dealing with the deep issues that have hurt us ALWAYS seem to fall into this same spiraling argument, I try and defer, to deflect, to steer it back, and keep it sane and keep the emotions out of it as much as possible, but inevitably she gets all pissed off at me, and ends up turning my unhappiness into something I should apologize to HER for.
Right now I'm working the 180 to build up my resilience and to show that I'm a strong MAN, and not some wimp who just allows his wife to love another man. The other man may have absolutely no idea how much she loves him, she may say that she would never ever go to him, she may even deny now that she does love him, but that doesn't make this any easier for me, to try and decide if this is worth the effort I am making to fix things.