Read this about 30 yrs ago, just re-read. Some of the language might be a little shocking today but my family was from rural Mississippi and I heard similar talk when I was young. What I'd forgotten was what a total SOB Patty's dad was, slapping her in the face hard enough to knock her down and beating her with a belt just for talking to a boy he didn't approve of. Her mom was pretty smarmy to her as well, although she would rarely try to calm down dad when he was on one of his tirades against Patty. Her younger sister was the princess of the family.
So given the lack of love at home it's not surprising that she felt an attraction to Anton. He treated her with more respect than her own family did. To the rest of the people in town he's just another Nazi who deserves to be locked up. So she was willing to help him, even though it came at a great personal cost. She is almost charged with treason and winds up at a reform school. Neighbors turn against her and because she is Jewish she is viewed as a traitor to her religion.
She was only 12 but she was willing to live by her convictions even though she knew there would be severe repercussions (Small Spoiler --> in the sequel you find out that her father has disinherited her).