role that needs to be taken care of. I think a possible underlying and not stated reason is because of Calpurnia's race. She would like to remove Calpurnia from the home so Cal doesn't have to hear some of the discussion that will occur regarding the trial.

Atticus refuses to let her go and lets Alexandra know that Calpurnia is as much of a member of the family as the rest of them. He notes that she has meant so much to the kids and him since their mother passed.

Alexandra does not feel that Calpurnia is needed since Alexandra is there, and she considers herself a better person to raise Scout and Jem. 

Scout doesn’t really care for her Aunt Alexandra.  Alexandra complains about her wearing overalls and generally disapproves of her.  She has also been heard to say very derogatory things about Atticus, since he is defending a black man.  Like many in Maycomb, Alexandra’s response to this is racist. 

When the trial is getting underway, Alexandra just shows up one day at the Finch house.  She is there to help her brother.  Despite her comments about Atticus defending Tom Robinson, Alexandra does care about her brother and wants to support him. 

Unfortunately, Alexandra does not feel that Calpurnia should remain since she is there.  Alexandra does not feel that Scout and Jem are being properly raised, since Atticus does not have a wife and the children are on their own with Calpurnia.  She tries to get Atticus to let her go. 

“Atticus, 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.”
“That’s what I am thinking of.”
“And don’t try to get around it. You’ve got to face it sooner or later and it might as well be tonight. We don’t need her now.” (Ch. 14)

Atticus disagrees.  He tells Alexandra that Calpurnia is not going anywhere until she wants to.  He knows she is part of the family, in a sense, and that they rely on her. 

This discussion comes up after Alexandra and Atticus learn that Scout and Jem went to church with Calpurnia.  Cal also offered to take them to her house, which Alexandra flatly refused to allow. As far as Alexandra is concerned, Calpurnia’s influence is not the one Scout needs.  She needs a woman in her life, but it needs to be a white woman who can show her the place in society she rightfully occupies.

The answer to this question can be found in Chapter Fourteen of this excellent coming-of-age novel. In this chapter, Scout overhears a conversation between Atticus and her Aunt where Aunt Alexandra advises Atticus that the time has come to fire Calpurnia. This conversation happens after Aunt Alexandra finds out that Calpurnia is going to take Jem and Scout to her black church. Note what Aunt Alexandra says to try and support her viewpoint:

Atticus, 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... You've got to face it sooner or later and it might as well be tonight.

Aunt Alexandra clearly believes that such a close relationship with an African-American is not desirable, especially for a young girl such as Scout who is growing up very quickly. Given the harsh realities of discrimination and racism in Maycomb, we can understand her perspective, even though her views are incredibly unpalatable from our 21st century viewpoint. Social standing and respectability at that time was built on a very clear understanding of the difference between blacks and whites.

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."

While it is not uncommon for Southern families to have a black maid, Aunt Alexandra apparently feels that Calpurnia exerts too much influence on her brother's children in areas that have nothing to do with her occupation.

One evening shortly after Aunt Alexandra's arrival, Scout asks her father what the word "rape" means. Atticus replies that it is "carnal knowledge of a female by force." This definition is one that little Scout probably does not understand, but it satisfies her. So she then asks her father why "comin' from church that day" Calpurnia told her to ask her father. When Atticus asks Scout to explain, she tells her father that they went to church with Calpurnia the Sunday that he was in Montgomery, and on the way home she asked Calpurnia about rape. Startled to hear that her niece and nephew went to a church with Calpurnia, Aunt Alexandra drops her embroidery into her lap and just stares at the children.

Then, because Scout does not understand her aunt's reaction, she innocently asks her father if she and Jem may join Calpurnia next Sunday. Alexandra interjects, "You may not." Scout disrespectfully tells her, "I didn't ask you!" Of course, Atticus makes Scout apologize, and Scout leaves the room. She overhears Alexandra tell Atticus:

"You've got to do something about her....You've let things go on too long, Atticus, too long."

It is then that Alexandra suggests that Calpurnia is no longer needed, but Atticus insists that she is a "faithful member" of their family. Clearly Alexandra does not agree as she seems to believe that Calpurnia has too much influence on the children, and she is not a suitable influence, at that.

The reason she says to get rid of Calpurnia is that she isn't needed any longer. However, Alexandra suggests getting rid of Calpurnia after Scout back talks her (Alexandra), and after there is clearly a disagreement about who is in charge and which rules Scout is to obey, so one can assume there's a power struggle, and a conflict over order.

Greg