Scout gets a new perspective on Aunt Alexandra when she silently thanks Miss Maudie for intervening in the conversation about the Robinsons.
When Mrs. Merriweather begins commenting on the Negroes in town, she is making an attack on the Finch family. The Finches are closely connected with the Negroes and the Robinsons in particular, and Mrs. Merriweather knows it.
"… Folks in this town who think they're doing right, I mean. Now far be it from me to say who, but some of 'em in this town thought they were doing the right thing a while back, but all they did was stir 'em up….” (Ch 24)
Mrs. Merriweather was basically saying that Atticus stirred up the Negroes, and was “misguided” in doing so. He and the people who supported them thought they were doing the right thing, but they were not. Miss Maudie decides not to stand for it, and intervenes. Aunt Alexandra silently thanks her.
She gave Miss Maudie a look of pure gratitude, and I wondered at the world of women. Miss Maudie and Aunt Alexandra had never been especially close, and here was Aunty silently thanking her for something. (ch 24)
Scout gets a new perspective on Aunt Alexandra because she did not realize she had the capacity to thank anyone. However, the reader realizes what is really going on. Miss Maudie is standing up for Atticus.
Previously we felt that Alexandra was just as racist as the others when Francis said she told him Atticus brought shame to the family. Here we learn that she does care about her brother, and not just the family name. Miss Maudie is not afraid to confront Mrs. Merriweather about her racism and hypocrisy, and Aunt Alexandra is grateful that she does it.