I need to make a Venn diagram comparing and contrasting Calpurnia from To Kill a Mockingbird and Aibileen from The Help.

Calpurnia from To Kill a Mockingbird and Aibileen from The Help are similar (the intersecting part of the Venn diagram) in that they both care for the children they watch (Scout and Jem in Calpurnia's case and Mae Mobley in Aibileen's case). They also function as surrogate mothers, as Scout's and Jem's mother has died, and Mae Mobley's mother, Elizabeth Leefolt, basically neglects her daughter. When Elizabeth does pay attention to Mae Mobley, it is mainly to subject her daughter to criticism, so Aibileen is the source of maternal care and affection for Mae Mobley. 

The ways in which Calpurnia and Aibileen are different (the non-intersecting parts of the Venn diagram) is that Calpurnia has a positive relationship with Atticus Finch, her employer and Scout's and Jems' father. Aibileen, through no fault of her own, has a troubled relationship with Elizabeth Leefolt because Elizabeth is essentially harmful towards her daughter and treats Aibileen with disrespect. Elizabeth fires Aibileen when her friend Hilly pushes her to do so, while Atticus would likely never fire Calpurnia. Another way they are different is that Calpurnia speaks her mind more freely, perhaps because Atticus allows her to do so, while Aibileen is more reluctant to voice her true feelings to Elizabeth Leefolt.