Victims of Psychopaths Community Group
Is he or she a sociopath or psychopath? Think we're only talking about serial killers here? Psychopaths, sociopaths and even narcissists come in every walk of life, every career level, and every socio-economic category.
I want to say that your daughter's impulse to confront wrongdoing is probably a permanent part of her personality and most likely derives from a strong moral character. As she gets oder, she probably will temper the impulse a bit as confrontation is not always effective or the best solution. You are right that Grey Rock or avoidance of the "friend" is the best solution. Not being associated with the girl would be the best possible outcome.