What is the theme in Lily's Crossing by Patricia Reilly Giff?

Lily Mollahan is a liar. Lily knows this, but no one else in her life is aware of the extent to which Lily is given to stretching the truth when it is convenient for her. Lily does not lie for malicious reasons. She simply cannot stop herself from making things up. In the beginning, her lies are fairly innocuous — she tells Gram and Poppy that Mr. Egan is an enemy spy. At another time, she tells Margaret Dillon that her Aunt Celia is a spy for the Allies living in Berlin. In chapter nine, Lily tells Mrs. Sherman at the bakery that Aunt Celia has frostbite so she can get out of the bakery in a hurry.