You know I trusted my daughter implicitly. It was everyone else I didn't trust. We raise our children with our expectations and most will live up to them. If you don't know all the teens (not kids anymore) well and feel comfortable then go with your gut.
I have read all comments and realize once again how lucky I've been. My child knew about boys, bees, and pollination (sounded better than just blurting out reproduction) since she was about 7. We spent many days discussing why it was so sad that many young girls seem to think that they had to allow liberties with their body to have people like them. She's got a very healthy self-esteem. She would call me to pick her whole group of friends up (male and female) from places they decided wasn't confortable.
You might let her start out at the party and give her a late cerfew and pick her up. Plan something important for the next day that she can't miss if she needs an excuse to save face. Offer to bring the LATE snacks, etc.