my best friend started doing drugs and I need advice

All she is doing is smoking weed but it's still drugs & I am not judging her whatsoever I am just so worried that something worse could happen to her I mean she's been my best friend for seven years. there is this guy that she has been friends with her whole life who judges her about every little thing & always shares his opinion even if she doesn't want it so she NEVER tells him anything that he could judge her for and I want to tell her to stop bc I don't want to see her get hurt but at the same time I don't want her to think I'm acting like him! Please tell me something I can say that might help bc I can't lose my best friend!!!!