I'm upset because my girlfriend and her family booked a vacation without me
Why did they book it without you?
Because they are stupid mother fuckers.
It's understandable to be mad when you've been excluded like that. You should tell your gf that it has upset you.
What's the point? If I speak to her I can't trust her. She's a stupid bitch.
I don't think you should get this worked out right now, though it's understandable to get a bit angry.