Alexandra primarily believes that since she has decided to come and live with Atticus and his family, Calpurnia is no longer essential to the household. Alexandra will provide the motherly touch that Jem and Scout need, she believes, eliminating this aspect of Calpurnia's responsibilities. Since Alexandra is a great cook, she will also replace Calpurnia in this regard. Alexandra also believes that Calpurnia has not done a sufficient job in turning Scout into a lady, and she tells Atticus that
"... it's all right to be soft-hearted, you're an easy man, but you have a daughter to think of. A daughter who's growing up.
"... We don't need her now."
Atticus will hear none of it, however. He believes Calpurnia has done a great job of bringing up his children. Besides, Atticus considers Cal "a member of this family."
"... Calpurnia's not leaving this house until she wants to. You may think otherwise, but I couldn't have got along without her all these years... Besides, sister, I don't want you working your head off... We still need Cal as much as we ever did.
"Besides, I don't think the children've suffered one bit from her having brought them up. If anything, she's been harder on them in some ways than a mother would have been... she's never let them get away with anything...and another thing, the children love her."