How could the heroine drive a car...

Maybe she was doing it illegally.

Sorry for the late post, but it was technically illegal. In the book, Lena is on the side of the road, in the rain, trying to get someone to help her. Ethan asks her why she didn't call 911, and she says she couldn't because she was driving the car illegally. Then Ethan tells her that she wouldn't really get in trouble in their small town.