Skeeter's mother's version of what happened with Constantine's daughter is told to Skeeter in Chapter 27. Skeeter has already heard of one version of this story, but it is important to her to hear it from her mother herself. Because Constantine's daughter has very light skin, she is able to pass as a white person, and she turns up to Skeeter's mother's house one day when she is having a meeting of the DAR chapter, with 95 women in the house. Constantine sits down and eats cake, chatting to the women around her. It is only when Skeeter's mother introduces herself to her that Lulabelle reveals who she is. When Skeeter's mother insists that she leaves, Lulabelle reacts in the following way. Note how the single word sentences and the incomplete phrasing communicates Skeeter's mother's outrage and shock as she narrates this to Skeeter:

Spit. In my face. A Negro in my home. Trying to act white.

It was clearly this offence, of "trying to act white," that upsets Skeeter's mother so badly, and resulted in Constantine being fired. Even though Constantine had not done anything wrong, the very fact of her relationship with her daughter, who has committed such a terrible crime (in Skeeter's mother's eyes), means that Constantine had to go.