Whats the name of this movie?

About three years ago, I watched this movie with mii older sister and it was about two thirteen year old girls that turned from good to bad drug doers, ers, and so on, like petty crime stuff, but I dont remember what it was called. At the beginning, they were getting high off of computer duster and hitting the crap out of each other. Please help, It was an EXTREMELY good movie!!!!!!