Why is annemarie worried about the Rosens in Number the Stars by Lois Lowry?

Annemarie is worried about the Rosens in "Number the Stars" because they are Jewish and the Nazis are targeting Jewish people during World War II. The Rosens are Annemarie's friends, and she knows they are in danger of being arrested or worse. Annemarie's family is also risking their own safety by helping the Rosens, adding to her anxiety about their well-being.