what would you do?? if your friend did this?

ok so the other day me and my friends went on a field trip. my firend hooked up with this guy on the bus and on the way back they started making out and toching each other all over. And now she is woundering why I am mad??? what should I do do I ever talk to her again??? I guess Im mad cause she gave her self away. which I shouldnt even care. but I guess since she doesnt care about her self it makes me not care about your?? I cant even look at her the same anymore