How does the author use foreshadowing in the novel, Want?

During her grad class, Elizabeth teaches Magda Szabó's book, The Door. The author uses the story of friendship and betrayal to symbolize Elizabeth's guilt. Before Elizabeth has even confessed the truth of what happened between her and Sasha, she describes in detail the events of Szabó's story, intensely invested in the way the main character abandons her best friend. Elizabeth's summary of the book foreshadows her coming revelation about Sasha's pregnancy and miscarriage, and Elizabeth's failure to support her.