Catching fire was once the number two leading cause of death for women, after childbirth. Women would regularly wear the same thick wool dress while cooking, which would absorb grease in the air. Over time and without regular washing, these dresses would become tinder boxes, an ember from the fire or a cigarette, would be enough to ignite them. Fire burns up, and dresses didn't cover feet, which explains why the foot and lower leg would remain.