Chocolate, I'm curious why you did nothing about your "separation" boundary. That was a pretty strong thing to throw down and I'm sure she had a healthy dose of fear about your words. Then came anger and a strong desire to find out if you were for real or not. So she started slacking a bit and you didn't enforce your boundary, she realized you were bluffing, she slacked some more, you did nothing, she lost respect for you. And here you are.
I think that when our spouse is trying to break a bad habit (cause, imo, I think that chronic "No" saying is as much a bad habit with some people as anything else--I realized I might get flamed for that but I believe it to be true) there will be times when we need to be supportive and encouraging in different ways. Right now, I am supportive of my H in positive and affirming ways and he responds well to that. In the beginning he would have taken this encouragement and sat back on his laurels and said, Well that's enough of THAT, and not tried any further. So in the beginning I had to really be on guard with the boundary firmly in place. I personally took this firmness too far and then had to spend time un-doing that damage but that's another story. I was just so paranoid about him not listening to me and, well, I do love the guy and felt sorry for him and was afraid that I'd shoot myself in the foot and accept less than I could live with, in the name of compassion.
Anyway, I think that at that critical moment, you BOTH gave up on the process. She did what's natural to a person trying to break a habit and form a new one..she did it for a while and then fudged back to her old, comfy behavior. You shoulda called her on it and enforced your boundary--or created a lesser boundary if you didn't truly want the separation. It is sad that we have to threaten our partners into meeting a fundamental marital need but look at it this way: You could have spent the last 4 years getting to enjoy her new hot body and sexy wardrobe. Instead you've let your own pride prevent you from saying, Wife what the heck happened? How can we get back to that place where we were both trying?
I had many, many, many setbacks with my H. I know that you have been around long enough to watch some of my more spectacular train wrecks. There may even be more in the future, who knows, I'm not a fortune teller, but I will tell you this: I wouldn't go back to the civil-but-sexless days for all the money in the world.