This is just my opinion, but it sounds like he's starting to wake up just a little bit. I would sit back and observe.
If he comes to you for assistance, I would simply say "h, you will need to decide how to handle this situation on your own." I think he doesn't trust her judgment and doesn't want her actually involved in the things that are very important to him. She's like a window dressing to his MLC life. Tossing the ow up in his face is a reminder of how much he's messed up the lives of everyone and it keeps the ow in his focus all of the time, which means he may stay w/her because there is no hope of reconciling w/you. By throwing up her name to him when he seeks your advice, it shows that you still harbor resentment and anger towards him and what he's done. Throwing the ow up in his face doesn't accomplish anything, except maybe make you feel better, but again, she's nothing but a window dressing to his MLC and if it hadn't been her, it would have been someone else.
I have a question for you...if he woke up, made all of the right moves, etc., would you consider taking him back? Whether you would or not, you will still need to co-parent and you both have children and activities that you both will need to participate in now and forever, i.e., marriages, grandchildren, etc. Hold your head up, back straight and remind yourself each and every day that you are the prize. The ow is nothing more than window dressing that can be changed out on a moment's notice if he should decide to attempt reconciliation w/you (that is, if you want to try to do so).
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
