Bruno's older sister, Gretel, undergoes a dramatic transformation throughout the course of John Boyne's The Boy in the Striped Pajamas.

Gretel is three years older than Bruno. She considers herself to be a great deal smarter and more mature than her little brother. Despite her self-professed maturity, she loves playing with her doll collection. Her dolls and enjoyment of playing with them symbolize Gretel's naivety and innocence.

As the novel progresses, Gretel's interests change dramatically. She develops a growing interest in geography, the events of World War II, and Nazism.

The stark change in Gretel's interests is emphasized when she parts with her previously treasured collection of dolls: "Gretel had decided that she didn't like dolls anymore and put them all into four large bags and thrown them away."

Instead of playing with dolls, Gretel turns her attention towards reading newspapers, collecting maps, and following the activities of the Nazi party. She replaces her doll collection with literature that promotes Nazism. She develops a romantic attraction to a Nazi soldier named Lieutenant Kotler. She uses maps and pushpins to track the events of World War II and the movement and activities of the Nazis.

Gretel's willing relinquishment of her doll collection symbolizes her transformation from an innocent girl into an obsessive Nazi supporter, although she is too young and removed from the war to fully comprehend Nazi beliefs and their consequences. The disposal of her doll collection marks a pivotal time in Gretel's life and a shift from child-like innocence to growing awareness of the horrors of the world.