My cousin (15) did the same. I just happened by chance to catch her before she got to her 4th packet, she got rushed to hospital and had her stomach pumped. Goodness knows what could have happened if I hadn't realised. I just hope the pills didn't have enough time to damage her organs.
I really don't think people are told the risks of Paracetamol overdose, it's very common and people should be made very aware of the consequences.