dont...its defintaly a dick move. if you see her start shooting heroin or meth...then let someone know (or drinking and drivning). but if shes jsut smoking or drinking...dont. its nothing major.
Personally, I HATE snitches. I've had too many bad experiences with them (mainly my lil bro who i have to live my life AROUND). Anyways, snitchin just pisses ppl off, and unless its life threatening , DONT SNITCH