How has Josef's mother changed since the beginning of the novel? Why has she changed?

Rachel Landau is the mother of Josef and Ruthie, and the wife of Aaron. Rachel is the reason that Ruthie survives the war. She, like Aaron, also inadvertently forces Josef to grow up. Rachel takes care of her family when Aaron is forced to go to a concentration camp. She then takes her children to the ship, secretly sewing their bank (her diamonds) in the seams of her daughter’s coat. She tries to soothe her husband, but it is to no avail. After Aaron jumps overboard, she is grief stricken and distraught, but seems to recover quickly. Josef finds her dancing alone on the ship later, and she tells him how she named him after her brother who died in World War I. Later in Vornay, when the Nazis are upon them, she offers up the diamond earrings she hid in Ruthie’s coat. When the Nazis counter that they will accept them in payment for only one child, Josef offers himself, relieving his mother of the choice of which child to save. Rachel dies in a concentration camp.