Don't act too suspicious around her, but notice things like if she sniffs in general a lot or does she have regular nose bleeds? Casually ask more about where she is going, who is she with. This is quite an expensive drug so keep an eye on her money amount. When she comes in and you suspect she has taken something, don't just let her run off into her room. Talk to her don't ask her loads of questions, just have a general conversation. Just do little things and if you find any of these positive maybe you should look further into things. Maybe sit down and have a convosation about it. Just remember to stay calm about it though. She's not going to open up to you if you just shout. I hope this could be some help. Good luck.
