I like Brand New Day's advice. If she wants the D, you go along but insist on your full rights with kids, house, money, etc. She's used to being in control here; you exercise some control, and the dynamic changes. Granted, she may still want the D. But if so you are going to get what is rightfully yours.
Yes, it's hard to contemplate the end of our M. We never expected it, and we don't want it. Yet it may well happen. At times like this I ask myself if I really want to be with the person I think my W is right now, and the answer is "No." Yet I confess there is a little part of me, and it does thankfully keep getting smaller, that imagines she could be someone different than who she is now and who she was. I needed to change, but I believe she needs to as well. I wonder if you are in the same spot--not liking what you see from her, but somewhere in you is a little voice, or a thought, that thinks there is a way out of this mess but you haven't found it yet.