Friend question??? PLease please help me?

I go to a high school and am a freshmen and have a group of friends. Today, some of them have been acting really wierd. I know the sone girl that was kinda acting snappy likely because of something going on with her and her bf and i just decided to stay out of it but from what i did find out from others is that she is going to a mixer with him and her two closest friends. Other people that i hang out with wanted to go to that mixer too and its not at our school. She doesn't want many people there it seems like but i don't know the full story. The others just many be in bad moods or something and just giving me the usual one word ****. So anyway, what i do want to know is what should i do to the friend that has the bf and should i just stay away, talk to her about it, or what? And for the others, how could you tell if someone is in a bad mood? pLease help.