I know you mean well, but there's a simple way we know drugs are not the case: We're so poor we can't pay attention. If she were using drugs, she'd have to buy them, and she is on a stricter budget than ever we are. We are in almost daily communication with her, and several dormmates, friends, her roommate and the dorm resident have contacted us with their reactions and suspicions. Drugs never came up.
I THINK YOUR BEST SENSE ON THIS ISSUE IS QUITE RIGHT. I'd be alert but I think your assessment is right. Especially outlining all the input from the diversity of those close to her that you're getting.