I will never understand what is going on in her head so why do I keep beating myself up trying to?
No, I doubt you would ever be able to understand her b/c I've been there and I have a hard time explaining. You are so focused on her, instead of getting a life of your own, and that keeps you constantly trying to figure her out. When you decide that you will enjoy life regardless of what she does, then you will get better faster.
Another reason it is hard to understand her is b/c this is so foreign to who she has been in the past, so you are trying to figure out what's going on in her mind. You just need to stop and decide what you will do for yourself....and "with" yourself. I don't mean that in a selfish way, but in a confident way.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!