Both Reddit and 4chan have demonstrated exceptionally well why this is a terrible idea.
In the specific case mentioned here, where state and Federal law enforcement won't take charge, why shouldn't she find a professional investigator to confirm who the perpetrator is, then use the same tactics he has used against her against him?
After all, law enforcement refuse to take action right? So it appears that law enforcement wouldn't care if she ensured that he is kept out of the picture.
(for the record, I'm playing devil's advocate)