At the end of chapter 15, what other character is Sally most like? What does Holden call Sally? why?
Holden is irrational and prone to spontaneous decision making that is shocking to others. For example, when he suggests to Sally that they run away to Massachusetts or Vermont:
"We'll stay in these cabins camps and stuff like that till the dough runs out then when the dough runs out, I could get a job somewhere and we could live somewhere with a book and all and later on, we could get married or something." (Salinger)
Sally is offended by the suggestion. She doesn't hate her life like Holden hates his. She has no interest in running away, she gets afraid when he starts screaming at her because she brings up legitimate concerns about young kids trying to survive with no money and no job.
Sally does not understand Holden's comments and he gets mad and says:
"You give me a royal pain in the ass, if you want to know the truth." (Salinger)
Then he gets scared because Sally is really mad and Holden thinks she might tell her father that he called her "a pain in the ass."
Sally is a Prep School student; she is similar to Stradlater, who was Holden's roommate. Sally puts up with Holden, similar to Stradlater. Sally doesn't understand Holden's serious nature, and they get along, same as Holden and Stradlater, until Holden becomes unglued and starts acting crazy.