Why did Anabella Pitcher decide to write My Sister Lives on the Mantlepiece? Can you tell me in a detailed paragraph?

Pitcher got the idea to write the book after watching a film about 9/11. After seeing the film, she thought it would be interesting to write about the event, not as it happened, but through the eyes of a child who has no memory of the event, and yet, whose life has been forever impacted by the tragedy.