There's all kinda precedent here.
There was a case a few years back where a High School got a great idea at a rally to haul out some blocks of dry ice and have a competition where the cheerleader who managed to sit the longest on the dry ice was a winner. Many tulips were lost: some to frostbite, some to lawsuits.
Yes, there is something to be said for personal responsibility. But when you hold and host a public competition, you need to do due diligence to ensure the fundamental well being of the participants. If you hold a marathon, you make sure the contestants know they are engaging in a risky sport, and you make sure they know what the risks are, and what the symptoms of severe medical problems are as well. You put that information at their disposal: it's in your interest too.
It's even worse when the whole point is to do something dangerous. Eating competitions have medical personnel at hand, and the contestants are briefed beyond "don't put your health at risk, but the winner will be the one who does".
The radio station in this case didn't consult a competent physician beforehand. They could have avoided a fatality by adding salt to the water. They could have had a chance at avoiding one by informing themselves what large amounts of water can do, and instructing the contestants on what it means to have a painful headache after consuming so much fluid.
They didn't, and they're gonna get sued. That's the tort system at work for you.
She may have been stupid, but the radio station was even more idiotic.
