What is distinctive about Cathy in The House on Mango Street?
Esperanza and her family live on Mango Street and it is a poor neighborhood. Outsiders look at it as a kind of ghetto. Esperanza meets different people, some of whom share her desire to get out of the neighborhood and have better lives. By no coincidence, Esperanza's name means "hope" - the hope of a better life; but she notes it also means "sadness" in Spanish. So, Esperanza has a nostalgia for Mexico but an increasing desire to achieve some kind of "hope" and that means trying to fit in in America (Mango Street). She realizes she lives in a neighborhood populated largely by minorities and immigrants, so she develops a camaraderie for some of her neighbors but always with the underlying idea that to be happy, she would need to move to a better neighborhood. But she never feels superior to her neighbors.
Whereas Esperanza is sympathetic to her neighbors and even friends with some, Cathy is elitist. She claims to have descended from royalty and she also claims that she will be leaving the neighborhood because she's too good for it. Cathy has something condescending to say about most everyone on Mango Street. At the end of the chapter, Esperanza adds that Cathy simply wants to move away from people like herself (Esperanza):
In the meantime they'll just have to move a little farther north from Mango Street, a little farther away every time people like us keep moving in.