Symbolism, Imagery, Allegory
When the book opens up, Wendy and her mother are in the middle of a fight because Wendy wants to go to California to visit her father, Garrett. Janet doesn't want Wendy to miss school, and Wendy thinks her mother is being mean and unreasonable and trying to stop her from getting to know her father.
Throughout the book, Wendy thinks back to this argument as something that separated her from her mother—something she regrets now that Janet is gone. But what she doesn't know is that she and Janet weren't really on opposite sides; before she died, her mother bought her a plane ticket and tucked it away as a present:
One more thing remained in the box. It was in an envelope. She opened it very slowly, undoing the top instead of ripping the paper, picturing her mother sealing it up all those months before. After this one last gift from her mother, there would be no more, ever.
Inside was a round-trip plane ticket, New York to Sacramento, with the dates left open.
"I shouldn't have given you such a hard time about this," she had written on the card. "A girl has every right to know her father." (34.35-37)
Excuse us while we tend to something in our eyes. Super touching, right? The last gift that Wendy gets from her mother is a kind of absolution for the fight they were having right before she died, enabling Wendy to finally move on, safe with the knowledge that her mother wasn't angry or disappointed in her at the very end. She was thinking of Wendy with complete love and understanding—and the airplane ticket proves it.