Talk to her about it. Tell her you care and you don't want her doing it. If you have to tell someone what she's doing to get her help... do it. Let her know that you did it because you care and you don't want her to get in trouble but you don't want her to do anything dangerous. Me n my boyfriend got each other to quit smoking pot, because we care for each other. And when you know someone really cares about you and doesn't want you to do that stuff, it makes you feel better so you don't do it and you also want them to be proud of you for not... Talk to her about it. Its one of the best things you can do... I know, I've been in her situation.