Why don't you take the initiative to go see her Grandpa without her, maybe send some flowers or a card or something to show you care in an indirect way. She has family, don't be a d!ck about it but separate yourself from her.
I'm sure I'm misunderstanding this, but are you suggesting that he will impress people by leaving his wife home and showing up at her grandfather's funeral without her?
As always John, you need to live your life, make your choices and live with the consequences. It's a lot different than giving advice to people you will never meet.
In my opinion, a mensch (good or noble man) puts aside petty differences and does what is right. You know what that is.
