How does the author use foreshadowing in The Face on the Milk Carton?

At the beginning of the novel, the author uses a play on names that foreshadows Janie's identity crisis. Having friends with more memorable names, Janie Johnson feels that her name is boring and tries to change it to Jayne Johnstone. After discovering the face on the milk carton, she then believes that her name is Jennie Spring.