In John Boyne's novel The Boy in the Striped Pajamas, nine-year-old Bruno's older sister Gretel undergoes a significant and deeply troubling transformation. For much of the story, Gretel is described as both obsessed with her doll collection and annoyed at the existence of her younger brother, whose disdain for his sister is equal to her's for him. To answer the student's question, then, Gretel spent most of her time with her dolls, her father's position and their relocation from Germany to Poland, and, more specifically, to the death camp the father will run, depriving her of the kinds of friendships that might otherwise occupy her time. The novel's unseen narrator describes an early incident involving Bruno's entry into Gretel's bedroom, only to observe her, typically, engaged with her "civilization of dolls."
Another reference to Gretel's obsession with her doll collection comes much later, when Bruno, lying on his bed attempting to read a book, is interrupted by his sister, whom he regularly refers to as the "Hopeless Case." The narrator describes this unusual event -- Gretel entering Bruno's room -- as follows:
"She didn't often come to Bruno's room, preferring to arrange and rearrange her collection of dolls constantly during her free time."
As Boyne's story progresses toward its tragic conclusion, Gretel's obsession switches from her doll collection to the war slowly but surely approaching every-closer to had been her family's sanctuary. Her interest in the war's progress, however, is not in the direction for which one would hope; rather, Gretel becomes a fervent believer in the Nazi ideal, and adorns her bedroom with maps from her father that she uses to track the war. This practice of tracking the war's progress on maps becomes a substitute for her doll collection. As the story's narrator describes this transformation:
"Gretel had decided that she didn't like dolls anymore and put them all into four large bags and thrown them away. In their place she had hung up maps of Europe that father had given her, and everyday she put little pins into them and moved the pins around constantly after consulting the daily newspaper. Bruno thought she might be going mad."
The answer to the student's question, then, is that Gretel first spends her time with her doll collection, but later discards the dolls and begins to focus her attention on tracking the war's progress, using maps and pins.