Of course you shouldn't deny her freedom. But please, don't think for a second that her girlfriends aren't gonna back her up. It's possible that they might be smart enough to realize that if they don't tell you what you want to hear, you'll forbid your girlfriend to go out. Which is ridiculous, because she can do what she wants anyway. And she will.
See... dancing with your girls is very different from going to a pub and then going home and crashing (sorry, it can get downright boring). Dancing you work up a sweat, you let go of your inhibitions and you enjoy the music. A lot more fun than just going to some bar only to pass out next to each other afterward. Unless it's a sexy bar
In which case sexy times can ensue afterward!