Don't be miserable and let her go. What's up with you? Depends what sort of girl she is doesn't it? If she's an absolute bike she could go into town and be bummed behind the print works. If she's got a bit of self respect she'll just go and have a top time and if she cops off, well that's life and you can't protect her all your life.
Don't believe everything you read about 18-30's. I went on a few in my late teens and the good thing was there would be a group of 30 odd stuck together for the week and if you like, looking out for each other too.
Stop being a tight sod and send her on her way with a few boxes of condoms, a packet of antibiotics and 14 morning after pills as a treat.