Tough call. If there were no negative consequences of reporting it then yeah, should be done but that's usually not the case. In the end, we're also assuming that this would be repeated which is an unknown as well. All in all, I'd say no one has the obligation to subject themselves to further crap because of a possibility of preventing something that may not ever occur.
I know that, but this girl had had allot of history with trying to get attention from doing stuff like that. She even wen't so far as to OD after she had an arguement and take a pair of scissors to her throat over her dad telling her she wasn't allowed to go out one weekend.