From The Book of Questions by Gregory Stock.

Question #81: If you were to discover that your closest friend was a heroin dealer, what would you do?

That would be pretty alarming and a little heartbreaking. I know she’s better than that and I would hope she wasn’t on it herself

I find it hard to believe I wouldn't know. If they were that type of person in the first place, we probably wouldn't be friends, but if we were, I'd probably let them be and just offer support when needed.

If they weren't that type, I'd let them know how much I disapproved!!

I would try to talk about it, and definitely distance myself from them if they chose to continue with it.
I'd also consider reporting to the authorities, heroin destroys lives and I don't want to enable it, but idk what I would actually do.

first, I'd try and find out if their situation was desperate enough that they'd resort to that to try and survive. If yes, then I'd do everything in my power to redirect them toward better things, and various assistance programs.

If no, then I'd call the cops on their ass.

I would try to help them to stop. because I wouldn't want them to do that.

i'll probably try to talk them out of it it can get pretty dangerous.

I already had to 'break up' with my closest friend over a severe issue that came to light. I wish we could've remained in some kind of strained friendship, but she had all intentions on forever defending the awful secret and drew a line in the sand that I wasn't going to cross.

If someone does something horrible that I can't morally condone and refuses any change, I guess I'm now ok with just dropping them, even if we were that close. Maybe they weren't such a good friend after all.