How do I keep my 15 year old daughter from living a life of sin?

She came home the other day and explained that one of her friends had brought "marijuana!!!" to one of the parties. I quickly told her that when I was her age I tried it, but, it was only because I was drunk. It tasted awful, the smoke burned my eyes, and it made me cough and gave me a terrible headache. After that I never, ever, ever touched it again. I even went to confession and told God I was sorry that I tried drugs. But, now I'm worried. What if she tries it and doesn't come to the same conclusion that I arrived at? I have other children in the house!! We can't have a pothead in the family! We can't! What would the neighbors say???