just a FYI guys, some people actually CAN handle drugs. been using drugs for years, done all except heroin (wanna wait till I'm older with this one). I am not addicted to anything (except caffeine ;p)
make SURE you KNOW what you're taking, make sure you dose properly, OBEY HARM REDUCTION RULES (!!!) and you'll be fine.
no, really, you'll be fine.
not every drug user is a useless junkie with no teeth, you can use drugs regularly and have a perfectly normal life.
now, with that said, DRUGS ARE BAD.
OP, I don't really know what advice to give you. she probably WILL be trying shit, whether you like it or not. If you are really concerned, best you can do is educate yourself on drugs and keep and eye on her so she stays away from evil shit like crystal meth and heroin. And don't panic either, I know a lot of people that tried weed and will never touch it again - just not their thing.
P.S. I know some of you people don't like to be reminded but alcohol is a hard drug.