Harriet the Spy: Genius or Idiot?

Did you ever read Harriet the Spy? Well, there is a part in the book where she is sitting in a diner or something and listening to the conversations there. After every conversation she guesses what they look like and what their connection was to the person they were talking to. And I believe that she was correct in labeling them except for in one case. I tried doing this multiple times and I failed miserably. After thinking a great deal about this failing I concluded that it wasn’t my fault that I couldn’t label them properly, it is because people are so different that even if a person might sound as being a fat, snobby, depressed woman, that person could actually be an anorexic, snobby, depressed woman. Therefore, Louise Fitzhugh, the author of Harriet the Spy, was never actually skilled in deciphering people based on how they converse with other people, she was mainly using stereotypes for Harriet so she could guess them easily and look like a genius to the twelve year old who was reading it.