Yeah, you're right. I think I need to talk to her about it. There are plenty of ways for her to bring it up without admitting that she's talked to me several times about lots of details. I do think that my W respects her mom a lot, hence the avoiding talking to her about it. She said that when my W stayed there last weekend, her reason was because we had been arguing a lot and she wasn't getting any sleep and that was all. Hell, they work together. She doesn't even have to say that she's talked to me, just that she's missed a lot of work lately, been acting weird, knows that we're having problems and she's her mom and she wants to talk about what's going on.
This is a start, but I still think it would be MUCH more effective to address the 500-lb. Adultery gorilla in the room.
Why not suggest to your MIL that she say "I know you've missed a lot of work lately, been acting strangely, and I know you two have been having problems, so I was concerned and asked CG what was going on. Please tell me the truth: are you really having an affair with another man, and carrying on in your and CG's home this way?"
Without addressing the adultery head-on, your wife is only going to lie to her mother. It's asking the farmer to ask the fox about the security of the henhouse.
