She was sitting in the driver's seat during the fire. This protected her back, the back of her shirt and her hair from the flames.
The front of her body was probably burned. The coroner listed the #1 cause of death as "smoke inhalation" and you could show no skin burns and still die of smoke inhalation.
Also she had a fractured sternum, the flat bone right over the heart that all the ribs join to, where her chest smashed into the steering wheel. A fractured sternum could cause damage to the heart which could cause death.
