How does Bruno's grandmother stand up for her personal beliefs against the Nazis?

when they're at Father's "promotion" party, the family,
which includes: Father, Mother, Bruno, Gretel, Grandmother, and Grandfather; they start
having a conversation about Father's "promotion". Grandfather talks about how proud he
is of his son. Grandmother on the other hand is not so thrilled. She says that she
disgraces it, and thinks it's inhumane.

Now your next
question would be how does this relate to the resolution of the
story?

It's ironic because in the end of the story Father
sees how Grandmother is right. When Bruno goes into the gas chamber, he dies and Father
realizes how killing innocent people, such as 8-year-old boys, is
wrong.