Have you talked to your daughter about this friend? Maybe your daughter feels uncomfortable with her but feels a sense of duty towards her, out of friendship, or is afraid to speak up for herself. At the end of the day, you daughter is a teenager, and as good and smart as she may be, she is bound to make some dumb teenage mistakes; we all do. I would be careful about telling her she can we see her friend, that's a surefire way to make her rebel and act out, but if she is mature and has earned your trust, as it seems she has, sit down and treat her like a young adult. Have an honest and open conversation with her. Let her know that you are wary of her friend, but that you trust your daughter to make the right decisions. That if she is confused as to what to do, to come talk to you first and you promise to try your best not to judge, but to help her navigate through the issue with support and advice. On the flip side, if she abuses your trust and makes poor decisions, deal out a fitting punishment. Make it clear that abuse of trust equals less privileges, while honesty and respect earn more privileges. My brother always lied to my parents and as such, had less freedom. I, on the other hand was always honest. Going to a party? Yes. Will there be drugs and/or alcohol. Yes, it's a possibility. Will you partake? No, I don't plan to, but if I do, I won't drive or go anywhere. Ok, let us know when you get there and when you are coming home. Because of my honesty, my parents trusted me, and truthfully, I lead a very boring teenage life because I never felt the need to rebel or act out because I had earned a freedom I didn't want taken away. So, long answer short, communication, reward honesty, keep an open dialogue, and so long as she acts like it, treat her like a young adult. Punish bad behavior and set boundaries when necessary, absolutely, but don't have a knee jerk reaction when she exhibits normal teenage behavior.