I posted a link above about land racers banning antifreeze due to flammability concerns.
And up beyond that, a link to problems with glycol mists in fire suppression systems.
Still very unlikely in this case, but water-glycol mists can ignite.
Something else happened here- it might even be that she was unconscious when the whole thing started since there was very little evidence of fire in the cockpit of the BMW.
Oh, yeah, and the explosion creates the evidence of BLUNT FORCE TRAUMA ~ you do get beat up pretty badly when you are "exploded" on by something.