I used Lulu's approach, make it hard for her to be in situations where she can drink ie- pick her up after parties, let friends stay at your house not her at theirs etc. One of DDs friend's mums picks her up from parties and then lets her drive home on her L's so that she has to not drink at all.

Its a difficult age, sorry actually the start of a difficult few years! I think you are already doing a brilliant job being open and honest with your DD, build on this relationship, talk with her about your fears, I found DD was always more responsive if I explained things rather than ordered her to not do something.

Big hugs to you, having had a 14 yr old and a newborn I know exactly what you are going through and trust me it does get better!!