Joy-Hulga, in "Good Country People", is a woman who is basically on the edge of a complete break with society. Given her education in philosophy, she can be found to be overly critical and abrasive against others. These characteristics, unfortunately, are solidified even more when she is left abandoned and legless by Manley Pointer.
Joy-Hulga is brash. She makes as much noise with her prosthetic leg as possible simply to irritate her mother. She does not care what others think about her; instead, she simply chooses to exist within her own terms.
Joy-Hulga is an introvert. She does not believe anyone to be good enough to place in her inner circle. She puts others down and harshly stereotypes all others around her. Joy-Hulga seems to be happy when she is simply left alone.
After her meeting with Pointer, her ideals about mankind are solidified even more. The one time in which she lowers the wall she has built around herself is the one time where she is hurt the most. She comes out of this (assumed given the story does not actually tell the reader) even more hardened against the world.