Returning to the main line (8) The car sits there overnight and the ethylene glycol slowly evaporates into the interior of the car (8) She comes down to the car early in the morning to go to the airport. (8) Hops in driver's seat, activates the ignition, broken light comes on ~ Bang, or (8) Hops in driver's seat, activates the ignition, catalytic converter heater tokes up ~ while she's fiddling with seatbelt and purse, checking mirror to make sure it and her lips are still there - Bang.
Doesn't matter if it was a broken light housing or the catalytic converter heater coil that got her!
The question I'm addressing is a simple one ~ how did it happen she had an explosive mixture of ethylene glycol and air in her car and garage ~ and that's how it happened.
It is always a good idea to provide some sort of ventilation to any garage where you park a motor vehicle. Store cans of gasoline OUTSIDE
So you are saying she starts up the car and sits there waiting in a running car with the garage door closed? If so she was an idiot.