I see you reading a lot into what W does, says, thinks, feels, etc...
IF you can go to the party and let all that go, then I agree with FY...Go, enjoy your family. Just don't put yourself in a position where you are looking for some sign of ANY kind. It was a really nice gesture of your MIL and it's wrong to allow W to dictate your choices...however, you seem to be reading a lot into W's actions/comments right now. Protect yourself first from more rejection and more obsessive thoughts...build a solid wall around your heart if you go.
Just my .02.
"You know, it's times like these when I realize what a superhero I am." Tony Stark/Iron Man
“Focus on what you can do, then do it with all your heart.” Lois Wilson