Hey @Anonymous (Lovely username by the way!)
Its beautiful to read you want to protect your daughter, but I understand that this friendship is very important to her. It can so tricky finding that balance when you think a friend might not be the best influence. We've got some info and resources for parents on peer pressure that could be worth having a look at here.
We also have this resource which is specifically about talking to teens about alcohol use, do you feel comfortable talking to her about these concerns? Or have you discussed drugs and alcohol with her before?
These conversations can be really difficult but can allow you to express your concerns with so she knows where you're coming from with your worries.
I'm also wondering if there could be any other avenues for your daughters sense of belonging, like a sports team or art class or something like that where she could meet other like minded young people. Does she have any interests/hobbies that could lead to meeting others?
Hope some of this is helpful, feel free to keep us updated with how you're going 
