How does she stand up for her beliefs?

She is ashamed of her son for wearing the uniform of the commandant. She walks out of his promotion party and really never makes up with her son even through the time of her death.

Grandmother tries to talk to her son (Bruno’s Father), but he will not listen, so she refuses to speak to him until he is willing to listen and walks out of his promotion party because she cannot stand to see him in his new commandant uniform after his promotion. This never happens before she dies, so she died with a quarrel unamended, and her son now has to live with the thought of what he did to her.