I think the word hypocrisy most clearly stands out to Maudie in this chapter. Here these women are supposed to be together in the name of service to this missionary, J. Grimes Everett who is serving a poor group of people overseas (likely black ones). But, all they are doing is whining about local blacks they could be personally serving themselves. They celebrate what the missionary has done, and likely take up a collection to help him. If they are the Christian women they say that they are, they would be the hands and feet of Jesus so-to-speak to those who need service right in front of them, their Negro servants.
The announcement of Tom's death was an ultimate climax for this chapter as she had just spent time being hurt by what they say.
Furthermore, Maudie deeply cares for Atticus. She is tired of him being the savior of this town morally. She wishes someone would join him in his plight to do right by all people, not just those with the right color of skin.
At least three things upsets Miss Maudie Atkinson at the Missionary Circle tea party. First, she is angered when the women suggest that Scout has a long way to go to become a lady. Maudie silently grips Scouts hand in a show of support. Next, she responds snidely after Mrs. Merriweather continues her rant about "my Sophie," her "darky" servant. When Mrs. Merriweather comments that Sophie ought to be happy with her pay of a "dollar and a quarter every week," Maudie snaps back at her. "His food doesn't stick going down, does it?" After Atticus arrives with the news of Tom Robinson's death, Maudie wipes away her tears and rejoins the tea party as if nothing has happened--a lady-like display that both Alexandra and Scout follow.
In this chapter, Miss Maudie is at the Finches' house with the rest of the ladies from the Missionary Circle. What ends up upsetting her at this meeting is the way that the ladies are talking about black people and about Atticus. Remember that this is just after Tom Robinson has been killed.
The ladies are all saying bad stuff about black people. They say that blacks just want to rape and murder, they complain about how their servants have been behaving badly. They talk about how blacks should be more grateful. They say Atticus and people like him just encourage the blacks to be uppity.
This finally gets Miss Maudie mad, especially because they are sitting here in Atticus's home, eating food that he paid for and a black person cooked, and they are saying this stuff.