Just be honest. Parents tend to forget about their days of wondering and finding out about sex. DO YOU REALLY want YOUR BABY to go behind your back. Sure you can say not right now, but be honest about what sex is, and the consequences. BE WILLING TO LISTEN. Communication about this subject is VERY IMPORTANT. If you want to keep yourself in the loop with your child you have to listen, and DON'T CRITICIZE. Young people feel very insulted then you criticize because it makes them feel dumb, and like less of a person (they are already struggling with an identity crisis and you fussing and demanding what they should and should not do will only make matters worse). DON'T BE NAIVE as a parent, and try to pass that on to your child. Sure no one wants their children to lose there virginity early, but you can't believe that just because you're ignoring talking about it they are ignoring thinking about doing it, because guess what IT WILL MAKE THEM WANT TO DO IT MORE. Its like curious George, no matter how much his owner told him not to do it, he still did (cursorily kills the cat). The more you talk the more options they have, the better the outcome.
As a parent of a girl, she really needs to understand her value as a women. Once she understands the power she has as a women to control the guys,she won't wanna have sex anymore, trust me.