What is the ultimate insult to Scout in Harper Lee's To Kill a Mockingbird? What convinces her to accompany Jem and Dill to the Radley Place?

Early in Harper Lee's To Kill a Mockingbird, the greatest insult Scout feels she faces is being told she is acting like a girl. One reason is because being a girl challenges her sense of identity since she prefers being a tomboy. But, the most central reason why she finds acting like a girl offensive is because, early in the novel, both she and Jem equate acting like a girl with being cowardly.

Jem first begins insulting Scout by telling her she's acting like a girl when Dill returns for his second summer in Maycomb. On Dill's first day back in town, Scout suggests they play by rolling in the old tire. Since Jem is angry with Scout, he pushes her in the tire with all his might, and she rolls right up to the Radleys' front step. When she is too scared to do anything but run, leaving the tire for Jem to retrieve, Jem says to her, "I swear, Scout, sometimes you act so much like a girl it's mortifying," which gives us our first clue that Jem and, therefore Scout, equates acting like a girl with being cowardly (Ch. 4).

Similarly, Scout is told she is acting like a girl all throughout that summer, and the insult influences her choices. More specifically, she gets told she is acting like a girl each time she questions the safety of Jem and Dill's actions with respect to their neighbor Arthur Radley, whom they call Boo Radley. On the last day of summer vacation, Jem and Dill decide to sneak onto the Radley property at night to try and get a look at Boo Radley. Scout feels the scheme is unsafe because, due to rumors and myths, she believes Boo Radley would kill them. When she protests, Jem insults her by saying, "I declare to the Lord you're gettin' more like a girl every day!" (Ch. 6). Since Scout equates acting like a girl with being cowardly, this insult is enough to make her feel she has no choice but to join the boys in their dangerous scheme.

Regardless of Scout's early understanding of acting like a girl, as the story progresses, both Jem and Scout come to associate acting like a girl, or acting like a lady, with courage, not cowardice.