Should I be okay with my girlfriend going to Dubstep concert without me?

Okay so me and my girlfriend have been dating for a few months now and i really do love her. The only problem we have had is I have a little trust issue with her. She had made some mistakes in her past, and slept around I guess you could say, but she has never given me a reason not to trust while we are dating. Tomorrow she will be going to a dubstep concert with a big group of friends, boys and girls, and there will be drinking, and rolling on extacy. If your not sure what dubstep is, its like electro-b, club music. I do trust her, it just really bothers me she will be taking extascy and be around a bunch of guys who could possibly make a move on her. She also dresses a little skimpy, and tomorrow im sure she'll wear some skimpy dress to the concert. I mean I know shes not cheating on me because we are always together and we are always hanging out so I dont want to be clingy so i let her go to this concert without me. Im kind of worried. I dont want to be controlling or smother her but is it okay that this bothers me? What should I do?