Chapter 12 is the chapter in which Calpurnia allows herself to be better known by Jem and Scout. This is the first time the children have been to church with her, and this leads to many questions and Calpurnia's honest responses.
One quote that shows a change in the relationship between Scout and Calpurnia show Scout's new ideas about Calpurnia:
That Calpurnia led a modest double life never dawned on me. The idea that she had a separate existence outside our household was a novel one, to say nothing of her having command of two languages (125).
This is Scout's first real awareness of Calpurnia as a separate person with her own existence. The reference to languages is about Calpurnia's ability to speak the Standard English of the household she works in and to speak the African-American English of her own race. This reference to language leads to another passage that shows the changing relationship between Scout and Calpurnia, in which Scout gains further insight into Calpurnia's character.
Scout, in discussing Calpurnia's capacity to speak Standard English and her not doing so among African-American people, says to her, "But Cal, you know better (126). Then Calpurnia goes on to explain that people do not like
...to have somebody around knownin' more than they do. It aggravates them (126).
I think Calpurnia's response gives Scout even more respect for Calpurnia, as Scout realizes that Calpurnia makes sense. This leads to another quotation that demonstrates the changing relationship.
Scout asks, "Calpurnia, can I come to see you sometimes?" (126). Calpurnia responds that Scout sees her every day. But then Scout expresses her desire to visit Calpurnia at Calpurnia's house and Calpurnia agrees. We can see from this section, too, that Scout is able to see Calpurnia as an individual, not someone who just takes care of Scout and Jem, someone whom she would like to get to know better in a different way, by entering Calpurnia's world instead of Calpurnia just entering her world.
Interestingly enough, Calpurnia's changing her speech to conform to the peope around her is an ability that people didn't think about very much when this book was written. Today, we call this "code-switching," and finally understand how important it is to be able to do this. After all, what is communication for if no one around you understands what you are saying?