Misery wrote:
I'm guessing it's a solution you'd rather avoid, but have you considered telling her parents or family members about it?
One way or another, particularly at that age, she could get in serious trouble doing that crap, which could hurt her for a long time. It might be in her best interests to inform someone like that about what she's doing. Even if it angers her.
Yes, you might lose a friend but save a life.
I think telling someone who can intervene and help her is the right thing to do, but of course it is "tattling" and doing things like that never won me any popularity points. Of course, not caring about what people think sometimes makes it easier to do the
right thing.