What does the status of the H and OW have to do with doing a 180? If she withheld sex before and didn't initiate and it was a big problem for H, then offering would be a 180 that would throw him for a loop. I'm not saying she does it all the time, but just throwing the bait out there to see if he takes it wouldn't be so bad. Plus if things were riding a positive wave, you increase the positive interactions slowly.
If, however, he has sex with her AND OW, then there's a problem. We don't know for sure if he's seeing the OW or not.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.