I agree, you can only go so far with these things, but people will take unnecessary risks with things even if you warn them about the dangers. In the end it has to come down to a mixture of sensible measures to prevent any accidental contact with potentially lethal voltages in normal day to day to use. The user also has to take sensible precautions as well when using anything that is plugged into a live supply and using leads with frayed and exposed conductors is a risk that need not be taken as charging leads are inexpensive and apart from the personal injury point of view, there exists the potential to damage the their expensive equipment due to short circuits etc, be it an iPhone, iPad or anything.
Common sense should kick in, of course this was a tragic incident and my heart and feelings go out her friends and family, but that does not alter that she took a risk, along with many others I suspect who go to bed with their phone under the pillows etc even though it is a well known fact that these devices can and have been known to overheat and burst into flames, the same has been know to happen with e-cigarettes as well.