This is very very tough!!

I think I would go to your Grandfather's party if I were you. For obvious reasons and what others have said.

Some people are just more vocal in their opinions than others. Sometimes it's easier for people to speak out loud about what they're thinking rather than holding it in. Also, some people seem to find fault with many things, whether they need to or not. I wouldn't relish the thought of someone putting me down either but I think you might regret it if something happens and you didn't go.

I think your BF's family will understand. Best wishes to you in this. I wouldn't want to be in your position.