Prius models do not have cigarette lighters.
Broken side car windows shatter into tiny pieces and do not leave large sharp shards as shown.
There's no way one charge of a cigarette lighter would have enough heat to burn through two seat belts without a recharge.
She is freezing cold however her breath does not show steam.
As her father leaves, worrying that she is freezing cold, he omits checking the backseat or trunk of the car for anything that could be used to sustain her life. Visible items in the car to keep her warm included things like the seat covers in the back & front seats. They would have created a warmth barrier.
They don't remember they have walkie-talkies until after the father jumped out of the car and can no longer reach them.