It all depends on how old your friend is, and how strict the rules of her house are. I can give you an example, looking back on when I was younger. My older brother had some weed, and I really wanted to try it but was too scared to on my own, so I got him to give me some and I brought it over to my friends house. We tried it once, and long story short my parents found out. Even though I was the one who brought it, I was grounded for three months and was not aloud to talk to those friends for a couple years. If they called my parents wouldn't let them talk to me and I had to sneak around and lie to hang out with them, because my parents felt they were a bad influence on me. Looking back, I was way too young to be making choices about experimentation, and deffinitly deserved the grounding, but if I were to sit down with my parents, and explain to them what happened, in a mature way, instead of throwing a fit and yelling and screaming, I would have probably avoided a lot of sneaking around and lying that I regret now that I'm an adult. As long as she sits down with them, explains what happened, and why, and if the rules of the house strictly say no smoking weed, and she respects the rules of the house, her parents could end up being a lot more understanding than you'd think. And besides, when you turn 18 you can do whatever you want, so why not try and make the next few years as painless as possible?