Aunt Alexandra rules a household rather imperiously and is stringent about adhering to the heritage of the Finch name.
An early reference to her aunt by Scout in Chapter 9 describes her as "cold and there" only. Later, when Aunt Alexandra arrives in order to take charge while Atticus busies himself with the trial of Tom Robinson and to bring feminine influence upon Scout as she is maturing, Scout finds her essentially the same:
"Put my bag in the front bedroom, Calpurnia," was the first thing Aunt Alexandra said. "Jean Louise, stop scratching your head," was the second thing she said.
In this same chapter, Aunt Alexandra instructs Jean-Louise--she refuses to call her Scout--in more ladylike behavior and dress:
Aunt Alexandra was fanatical on the subject of my attire. I could not possibly hope to be a lady if I wore breeches; when I said I could do nothing in a dress, she said I wasn't supposed to be doing things that required pants. Aunt Alexandra's vision of my deportment involved playing with small stoves, tea sets, and wearing the Add-a-Pearl necklace she gave me when I was born; furthermore, I should be a ray of sunshine in my father's lonely life.
It is not long before Aunt Alexandra assumes her place as matriarch of the Finch family. She directs social activities such as the Missionary Tea, she has Scout wear dresses, she instructs the children on the shortcomings of others and the superiority of the Finch lineage as she is very preoccupied with the importance of heredity and the caste system of the South. She is adamant that Jem and Scout live up to their family name and preserve the dignity of their heritage. So, she insists that Scout speak to any of her lady friends who come to tea or to visit. And, she objects strongly to the influence of Calpurnia on the children, disapproving of their close relationship with this maid, their accompanying Calpurnia to her church, and other interactions with her. In fact, she speaks to her brother, suggesting he dismiss Calpurnia, implying that her relationship with the Finch children is inappropriate.
Clearly, Aunt Alexandra comes to the home of her brother, with her imperious style, with the intention of correcting the lack of decorum and of making Jean-Louise into a little lady and the children and even Atticus more aware of their heritage.