What is the purpose of the story about Jeannette falling out of the car?

While driving away from the casino, Jeannette falls out of the side door of the car and tumbles down a desert hill, bloodying her nose and getting pebbles and debris stuck in her skin. She waits for a long time by the place where she fell, fearing that her parents might abandon her. When her family finally returns, Jeannette refuses a hug from her father, blaming him for trying to leave her behind forever. I think this is just another example of her parent's complete disregard for anything coming close to responsible parenting. There is a sense that her father and mother are oblivious to their daughter's safety and sanity.