You're not upset with your gf, and your gf is not the one causing this. I wouldn't talk to her about it and expect her to be able to do anything about it. You can vent to her about it, yes, but I wouldn't approach it as though it's your gf's problem. Can you talk to your group of friends? They would be the ones to speak about it and the ones to bring the issue to their attention. Either that, or stop hanging out with them as much. I would tell your gf that there's nothing she can do about it and it's not her fault, the next time it happens. This is all on your friends. And yes, it's very rude. If it were me, I wouldn't hang out with them as often.