Aunt Alexandra's arrival changes Jem and Scout's lives in a number of ways. She brings a sense of order and discipline to the household, which is something that Atticus has been unable to provide. She also brings a sense of tradition and respectability to the family, which is something that Jem and Scout had not been exposed to before. Aunt Alexandra teaches them the importance of manners and proper behavior, as well as the importance of respecting their elders. She also serves as a role model for them, showing them how to be a proper lady and gentleman. In the novel, Aunt Alexandra represents the traditional values of the South, and her presence serves to remind Jem and Scout of the importance of upholding these values.