The other day, I was invited by my girlfriend to her family's pre-4th-of-July barbecue, which was taking place later the same day. It involved her mom's side of the family, and about 15 relatives came. I was the only non-relative invited (and by her specifically), and she thought it would be nice if I could meet her extended family for the first time.
Given that it was such short notice, and that I had planned to spend some time with my parents later that evening, I told her I could only spend 30 minutes to an hour there, even though I certainly wanted to go. She felt that it would be rude for me to stay for such a short amount of time, and said it would be better if I didn't go at all.
In the end I decided to go to the barbecue and stay for about two hours, after talking with my parents. I had absolutely no desire to be rude, and as it turned out, I was well-received by my girlfriend's family. However, I was still a little unsure about what I should have done.
I'm a college student in the United States, and we've been dating for two years. I already knew her parents, and I had briefly spoken to some of her other relatives, but I didn't know them well. Under these circumstances, would it have been rude for me to just spend 30-60 minutes at the barbecue, explaining the reason to my hosts? I think it was certainly safer for me go, but would doing otherwise have been a breach of etiquette?