Either the server didn’t relay that to the kitchen, or the kitchen didn’t do their due diligence. But either way, someone employed by Disney seriously fucked up, and a person died as a result.

Given what I know about the restaurant industry, the chef probably thought the lady was just being "bratty" and made up her allergy to get a "special order", and ignored the substitution request. Sadly I know too many "proud chefs" who just straight up ignore these things and the consequences when they trust their instinct instead of the order is

That said, I've also heard of careless wait staff.... had a friend of a friend go to a restaraunt and order diet coke. He felt light-headed after his third glass and realized his coke tasted "off", when asked the waitress just told him

"Oh, I just went ahead and gave you regular since you're kinda skinny anyway."

Bro was skinny yes, but that's not why he ordered diet. He was actually diabetic and had to go to the hospital to avoid dying as the "light headedness" was his body starting to going to shock.

Needless to say, she was fired and the restaraunt was sued for the medical bills.