Why does Bruno call his sister Gretel a "Hopeless Case"?

Theof
Boyne's novel is a nine-year-old German boy named Bruno. Bruno is depicted
as a small, naive child who has difficulty adjusting to his new life in "Out-With,"
which is how he pronounces the notorious Auschwitz concentration camp. Initially, Bruno does not
get along with his domineering sister, Gretel, who is three years older than him. Bruno calls
Gretel a "hopeless case" throughout the story because she is mean, arrogant, and
insensitive toward him. Gretel is not a loving, compassionate older sister and does not get
along with Bruno. She continually corrects him, does not allow Bruno inside her room, and views
him with contempt.

By giving Gretel the name Hopeless Case, Bruno is
expressing his derision toward her and stating that she will never change her ways. A Hopeless
Case is typically someone who will never amount to anything or transform into a better person.
As the novel progresses, Bruno's sister lives up to the name, as she ignores Bruno on a regular
basis and refuses to take him seriously. Eventually, Gretel begins to mature and spends the
majority of her time studying, doting over Lieutenant Kotler, and keeping to herself. Bruno ends
up feeling bad for the Hopeless Case because she does not have a genuine friend like Shmuel to
keep her company. Overall, Bruno refers to Gretel as a Hopeless Case because he does not believe
she will ever mend her ways or transform into a kind, understanding older
sister.