The fact that she even told you says alot.
That being said, think of it this way, by the times kids are teens, they're gonna make their own decisions, whether we like it or not. Hopefully, by that time, all the parents have taught the child to have enough common sense to know when to say no, but they will do what they want to with their friends. Keep the lines of communication open. If you never let her out of the house again, she'll continue to do whatever it is she'll do, only you won't know about it and you won't be able to talk her through it , help her think it over after, know what I mean?
Btw, I was a teen who's Mother gave me no breathing room at all. I mean, in all seriously, I wasn't allowed out of the house, and if I was, even up until I was 17 1/2, she insisted calling my friend's parents and talking to them, making sure they'll be home and supervising the entire time, if I wanted to go somewhere. Did that stop me? Nope. I skipped school to try smoking and pot. I lied that I got detention, so I'd have an excuse to be late coming home from school, in order go to friends houses and walk the train track bridge (the cool thing to do at the time). Later, I lost my virginity when my Mother thought I was at my afterschool job. On sleepovers, me and my best friend would sneak out of her bedroom at midnight and hang out all over town- it was the bad section of town. Heck, when I was barely 15 and my best friend was still 14, we snuck out of her room with two 26 year old guys- they took us about 45 minutes away to an empty house by a lake. My friend and her date were sniffing cocaine, drinking, and "doing their thing", if you know what I mean. My date was a little more tame- we just talked. Thinking back now, I shudder to realize that it was the perfect setup for us to be forced, kidnapped, killed, whatever. If I'd had a Mother to talk about these kinds of things, and the freedome to so SOMETHING, SOMETIMES, I'm pretty sure I would have known better than. Keeping the lines of communication open and giving a little freedom are so important.
I pray for the day Family Court recognizes that CHILDREN have rights, parents only have PRIVILEGES. Only then, will I know my child is safe.