Their response to a warning that what they're doing will, or could result in death does count. What matters is the rational content of the warning. It doesn't matter if the caller was a construction worker.
Regarding something like global warming, it doesn't matter how they respond, because there's no direct risk of injury, or death.
Re: GW
"The fact is that, depending on your beliefs, it doesn't make any of it true."
The mechanism is real. Otherwise, it's the magnitude of the effect that's important. The magnitude of the effect is small an inconsequential. What anyone in particular believes is irrelevant, regardless of credentials. It's the facts that matter.
I believe that a court of law will only accept such a warning as credible if it comes from an industry professional such as a doctor, registered nurse, licensed ME, etc. I beleive that a court would take such information under advisement if it comes from an orderly, and it would make note of the fact that a warning was provided by a construction worker but, under those conditions, since neither individual is considered an industry professional, such information content does not impose an obligation on the individual receiving the warning to act on it. In those situations, the warnings are considered opinions rather than medical fact. An, an opinion is what the DJs offered when they told the deceased that they didn't think her headache was important. The content only has meaning when such warning is issued by an individual who can prove to a court that they are qualified by profession to issue such information on the basis of proven medical fact.
And, the term "medical fact" has a myriad of interpretations in the medical profession. Medical fact tends to be tempered by both known and unknown pre-existing conditions. A "normal" person with no pre-existing conditions may be able to tolerate drinking 2 gallons of water (despite the potential for medical damage later) far better than someone who is diabetic or has a heart or blood condition. It's all a matter of degree.
Look, I know that you want to punish someone for this incident, and, in a way, I understand your point. But the fact remains that the deceased had the option of participating in the contest or not. And, as a participant, she has an obligation for her own health, safety and well-being. If you believe that she was blameless in contributing to or causing her own death, then you have to believe that humans are incapable of being responsible for themselves. That means that when you get out of bed in the morning, you don't get dressed until the weather guesser tells you exactly what to wear. And you don't eat or drink anything until the radio or TV nutritionist tells you exactly what you should eat or drink. And you don't go out of the house until someone in authority tells you that you have to go to work, school or the store. Etc., etc., etc. Frankly, I don't believe that you think any of those things, otherwise you'd have thrown the HillaryCare argument in just to stir things up.