My mum had a rule in our house which was no boyfriends until we were 15. Because then we were old enough to have a relationship and understand what it means to have one. We were also old enough to go on dates and what not. She also had another which was no sex until we were 18 so then we were old enough and mature enough to deal with what comes with sex but of course me being me i didnt abide by that rule

I think in this situation let her know that you are open to the idea as im sure at this age they wont be doing anything. And just let her know that you trust her and so she will come to you if anything happens (he pressures her for sex or that sort of thing)

Hopefully it is just one of those 'my friends are doing so i want to too'