First you haven't done anything wrong in the eyes of God.
Second, she is a player, keep your distance. By player, I mean she likes to get as many guys attention as possible and usually ends up breaking their hearts.
Third, I say let the smoking go. She is young and we all make mistakes. If it isn't habitual, then even if you turn her in, it won't change anything. They will give her a talk and let her go. They won't tell her anything she doesn't know. She is human, she made a few mistakes, let it go.