This was not a kid. This was a 28 year old woman. That's the part I don't like. "Fly out the window like Superman, lady!" If she does it, why shouldn't she be held responsible for her own stupidity?
What is the difference between a young child that might not understand the difference between fantasy seen on TV and the reality of gravity and an adult that might not understand the complex and, to the non-medical layman, rather esoteric topic of serum electrolyte homeostasis?
Not much.
Each case does not constitute “stupidity” but an age-appropriate lack of knowledge about a particular subject.
You yourself stated that the activity “was not inherently dangerous”. That does not make you “stupid". It only makes you uninformed about a specialized subject I deal with professionally for a living.
Whatever you do for a living, I am certain that there are several aspects of it that are obvious to you that I will be completely clueless about. Again, that is not an example of “stupidity” but a lack of specialized knowledge.
If someone encourages others to engage in a dangerous activity, they are liable as the danger may not be at all apparent to the averagely intelligent adult they are encouraging.
Take, for example, an eating contest to eat two pounds of liver cooked as liver and onions in less than two hours:
Sound reasonable? Dangerous?
Since I am an avid hunter, I give each contestant a choice of beef liver, duck liver, lamb liver, elk live, deer liver, black bear live, polar bear liver, grizzly bear live, buffalo liver, zebra liver, antelope liver or cougar liver.
Sound reasonable? Dangerous?
Which liver would you pick?
Does the choice make any difference at all?
Are you "stupid" if you do not know the answer or if the question never even occured to you?
The answer is that if you pick the polar bear liver you will have ingested twice the lethal amount of Vitamin A at one sitting.
If I know that and allow the liver eating contest to proceed, I will probably be prosecuted for murder. My victim would not be "stupid". He would merely be uniformed about an extremely esoteric but potentially deadly subject.