How did Bruno try to conceal mentioning Shmuel to his sister?

Bruno tried to conceal mentioning Shmuel to his sister, Gretel, by avoiding direct references to him and their friendship. He understood that their relationship was forbidden due to their differing backgrounds and the tensions surrounding their lives. Instead of openly discussing Shmuel, Bruno would speak ambiguously and change the subject whenever Gretel brought up topics related to the other side of the fence. This secrecy highlighted Bruno's internal conflict and desire to protect their friendship from his family's prejudices.