Hi merrick and welcome to piecing ... I haven't had much time this week to visit here on the board, but when I saw your first post here ... WOW ... how that brought back some memories. While I have yet read any past details, I saw many parallels in where I was two years ago and where you are now.
Your WAW is right now looking for anyway to continue to fortify you as being the villian for everything that has gone wrong up to now in order to continue rationalizing her choosen course of action. However, she has noticed the changes you are making and the first "knee-jerk" reaction is anger. Anger in that after she has made her choice that M cannot be "fixed" and now its time to move on, that you had now picked this time to work on making M better. She will get over this in time as she starts to see the changes are REAL ones and not just a facade.
Your focus now should be on taking yourself out the above equation. Diffuse or at the very minimum deflect the anger and the blame. Continue to validate. Let the pointed attacks go, walk away if you have to, but remain calm and polite if not even pleasant. Try to keep your responses short and direct, such as when she asked about how would you have a good time at the party ... a simple reply would have been that you are only looking to enjoy spending time in the company of your friends for the evening and you are confident you can do that despite the current sitch.
That's I have time for right now ... but if you're interested in seeing a sitch like this can turn around take a gander at: Get out of jail FREE!
While I have yet read any past details, I saw many parallels in where I was two years ago and where you are now. 
