Thanks for the feedback!!

" They are the ones causing the problem, not your girlfriend. "

Oh, I know.
Did it sound like I was blaming her?
No, she has no control over it at all. She's been wonderful. It's all on them, not her.

" Why would you want to go and be with people who ignore you like that? "
Because she enjoys spending time with them. Sometimes we have to tolerate certain people in order to keep our partner happy.
I've known people who don't like their inlaws, at all, but they still attend their spouses family functions in order to keep their spouse happy.
Know what I mean?

We all go see the same local bands on nights that they play.
So, I could tell my gf that I'd really rather not sit with those people like we always have when we're all there, but it would create a lot of confusion and I'm worried that it would just
make the situation worse.

I'm NOT going to keep putting up with being ignored, though!!
I just have to figure out how to tactfully talk to my gf about this.
That's why I'm seeking out advice.

It would be nice if, after I have discussed it with her, she sticks up for me and tells her gf's that she doesn't like the way that they treat me!!
That would be appreciated.