unless somehow they didn't mention, but she had a gas leak and in the midsts of getting run over, she got gas poured all over her, and at the same time, decided to get ready to smoke a cigarette and go ahead and light her lighter, while getting run over, no cigarette in mouth, and the flame ignited the gas that had dripped onto her vagina, burning it, right before the tires ran her over, also extinguishing the flame.
but I doubt it.