Cathy is the first friend Esperanza meets when she moves to Mango Street. She tells Esperanza that she is related to the queen of France, which of course is a lie, and that her father will one day fly there to inherit a family house. This type of lying suggests that Cathy greatly needs to feel accepted for more than who she really is. She probably feels a little like Esperanza--dissatisfied about living on Mango Street.
Next, Cathy gossips about people in the neighborhood by telling Esperanza who to get to know and who to stay away from. Usually when people gossip, it is to show someone else how important they are, but they come off sounding impolite, self-righteous and thoughtless because they make assumptions based on little or no evidence to what is really going on. For example, Cathy tells Esperanza that there are "two girls raggedy as rats [who] live across the street. You don't want to know them" (12). Cathy is referring to Rachel and Lucy who actually become Esperanza's good friends when they buy a bike together. Cathy bases a person's worth on what they wear and how they look rather than on good character. Luckily, Esperanza can look past Lucy and Rachel's clothing and become good friends with them.
Finally, Cathy is a thoughtless gossip again when she criticizes Alicia. She says that Alicia is "stuck-up ever since she went to college. She used to like me but now she doesn't" (12). If Cathy thought about other people as much as she thought about herself she might realize that Alicia's going to college is a great thing! She doesn't have time to socialize with Cathy because she must get up before sunrise to make tortillas for her family before attending school all day long.