Does my friend have any reason to be pissed and upset?

I can see how she's a little hurt - she always thought of you guys as "the group", but she was at the family's anyway. What were you supposed to do? - Nothing??? The way I see it, she got to hang out with her family whom she rarely sees, and you hung out with friends - a win-win situation. She's just hurt that she wasn't included, but I think she needs to get over it - there will be many more opprotunities for ALL of you to hang out.