Compressing her organs as only a queen can.
How It Could Kill You:
The act of donning a corset didn't actually become truly dangerous until people started tight lacing them to the point that their insides were squeezed like a toothpaste tube.
Unsurprisingly, when tight lacing was fashionable people didn't breathe very well. With their liver in their throats and their lungs in their bellies, Victorian women invented "the heaving bosoms." Breathing the wrong way in one of these things could break a rib (a serious injury in the days before anesthesia) and cramming all of the organs inwards could cause internal bleeding. Female impersonator, Joseph Hennella, was doubly unfortunate when, in 1912, he first collapsed on stage as the result of the tight lacing from his corset, and then when The New York Times wrote the part about what killed him, they said it was his "increasing girth."
In 1903, a woman died suddenly due to two pieces of corset steel that became lodged in her heart. Yeah, when your outfit fucking stabs you to death, it's probably a sign that you've made a bad fashion decision.
What the Fuck Were They Thinking?
What else do you do when you live in a society that demands women have a shape that's physically impossible? They were stuck between wearing a thing that could snap ribs, or a ridiculous cage dress that could fling them into oncoming traffic at the first gust of wind. At that point, you just flip a coin and wait for someone to invent feminism.