One thing I've learned is that predictions of the future are subject to drastic change as time goes by.
Your W is in a deep dark hole. She wants a D. That's right now. If she starts the process of going forward with the D, that's her choice. You need to live for YOU. These events are out of your control. A month from now, or two months, or six months, things may be different, in fact they probably will, because they always are. Does that mean your M has a better chance? Who knows? Sounds like the only direction is up from where she is, so at this point change is probably good.
My point is, you can only control YOU. Detach yourself and your life from her. If you have to, try to put yourself back in time to before you met her. Try to be that person again. Or, if you really have to, imagine what you would do if she died. Then you would HAVE to live for you. She has a journey to travel, without you. Let her go. Maybe the future will bring her back to you. Your best chance to have that happen is to be a great person, so when she comes out the other end of the dark tunnel she'll see how great you are.
There is a popular saying here "Believe nothing they say and only half of what they do". I have found it really is true, although after living it, I would word it "Everything they say is subject to change, but changing after doing something drastic, like moving out or having an affair, is harder, but not impossible".
