You need to understand that everything about is about her. At least, in her viewpoint it is about what she needs and wants. You will see more selfishness in her than ever before. The only time it is about you, is when she tries to turn the table and make you out to be the bad guy. That's why you can't get into R talks or trying to explain where you stand. She doesn't care. She only cares about what she gets out of it.
She needs to get this........the minute she decided the two of you would not be man and wife, that's when it ceased to be a family unit. You will no longer be doing things as a family! That information needs to hit home with her, and hard. She doesn't get to have both the family and the single life.
You don't have to show proof of anything. If anyone should be held accountable of their actions or show proof, it should be her showing you. She is going to twist this around and make it your fault that she had an A.
I garantee you that she will twist everything you try to say and do. That is why you have to stay focused on your plan of action and not on her. She'll make you believe the moon is made out of cheese, if you listen to her. It's crazy.
The upcoming birthday celebration.......if it is the kid's birthday, you just tell her there will be separated celebration parties this year. If it is her birthday, you do nothing for her. If it is your parent's, she is not invited. She doesn't get to lay down the rules for you or your family. She will have to give her kids a birthday some place else, and without your help. You will give them yours. That is what divorced families do!! She chose to go outside the M, and she wants a D.......so show her what that will be like. It is no longer one big happy family, and it is not b/c of you......it is b/c of her.
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!