Behind the reason that Aunt Alexandra thinks Atticus should dismiss Calpurnia is that Scout is becoming too friendly with African-American people and wants to visit Calpurnia at her house.
Aunt Alexandra tells Atticus that since she has moved in, they can dismiss Calpurnia. Atticus said that Calpurnia is already part of the family and the children see her as something close to mother. I think so tell me if I am wrong.
