<human>: Hi there people of reddit. Soo a new girl moved next-room to me and she's great. Except for the fact that she smokes weed. I can tell the smell almost immediately and she's the only person here who obsessively locks her door (even though the landlord would never enter her room without asking her).

I don't want to immediately out her to the landlord because I want our friendship to remain intact. How do I carefully tell her that she can't smoke here? I mean for god's sake we can't even have candles or incense, never the less a drug that is illegal in my state. 

Any help is appreciated.

Can you summarize the given text in a few sentences?
<bot>: Nice housemate smokes weed, a lot. How do I tell her/ask her to stop doing it tactfully?