There you go then.
A tragedy? Certainly. But was Monster really responsible for her death? There are probably a thousand other consumer products out there that would have proven just as lethal to this young girl.
Perhaps if Monster sold itself as some sort of "health tonic", the girl's family might have a case. But that's hardly Monster's image. Monster's packaging and marketing clearly promotes it as an "edgy" product.
Personally, if I had been diagnosed with the kind of issues this girl had, I'd avoid products such as Monster. (I'm personally quite healthy, and I avoid products like this anyway) But we also know that teenager's ability to assess risk is marginal to non-existent, as it clearly was in this case. Was this Monster's fault? The court will decide.
Personally, I'm willing to bet that Monster will prevail.
As for the "should they be regulated" issue; I've already said that if we're going to regulate Monster-like drinks on the basis of 5 deaths per year (and most of those deaths were due to extreme circumstances) then there are probably thousands of other products/activities we should be regulating as well that are killing far more people.