Major Goof ?
The girl dies following an argument with her boyfriend. They've been making love in his car having pulled off the main highway onto a dirt sideroad. Its winter and the roads are covered in snow. He tries to drive away and the car gets stuck. The more he revs up the engine the deeper the car sinks. They both get out and he tries to free the car. She berates him for being puny and unable to jack the car up. He hits her, she falls on the carjack and dies. So there he his, having killed his girlfriend, she's lying in a pool of blood and his car is up to its axles in snow.
Next thing we know is that the car is back home in his Father's garage.
So how did it get there ?