I imagine it was a small lie that got out of hand. She did not mastermind a media storm. She told a lie to her school or her parents, they went to police, police talked to media, media interviewed the family, etc. At some point, if she were an adult, she would have understood that the lie had gotten out of hand and would have put an end to it. She was probably so afraid of "getting in trouble" that she didn't dare admit she lied in the first place.
When I was in kindergarten, I once lied about seeing a snake in the schoolyard. I don't remember why or how, I just told a stupid lie like every stupid kid (which is the same thing as every kid) does all the time. Now, no one believed me and I don't think that anyone else in the world remembers what I said, but imagine if they did. Imagine the grown-ups had taken it seriously and called 911 (well, 125 realistically , it wasn't in North America). The city would have started a large investigation to find the missing killer snake, the media would have printed article after article reporting on how people should be scared of sending their kids to school when there are dangerous animals on the loose and no one does anything about it, recess would have been cancelled, ... Imagine a shark scare, but on a larger scale. Every now and then, some grown-up would have asked me if I was sure I saw a snake, and due to the aforementioned stupidity, plus the fact that I was afraid of getting in trouble, I would have nodded yes. It would have been The News until something else distracted people from it.
None of this happened because no one believed me in the first place. But if it had happened, should I have been held criminally responsible for all the trouble?
That's my point. Kids lie all the time for all sorts of reasons. If you want to start holding them responsible through criminal justice system, you would have to send every one of them to jail.