Susan Kushner is a little girl with long blonde curls. Ramona first meets Susan in preschool, in Beezus and Ramona, and when Ramona starts kindergarten and when she first pulls her hair, they become rivals through much of the series. In Ramona the Pest, Susan's S's look like worms crawling, as many students with S's in their names in Ms. Binney's class. Although, in the first edition of Ramona The Pest the book describes Susan's hair color as, "a sort of reddish brown".
Susan is portrayed as being somewhat snobby and overachieving; in the book of her debut, her beautiful curls become the object of Ramona's fascination and lead to the girl's suspension from kindergarten for pulling the curls out of curiosity. In the following book, set a year later, Susan copies a stereotypically-designed wise paper bag owl designed by Ramona during an arts and crafts session, which is destroyed by an enraged Ramona after Susan is praised by the entire classroom for her work. She is depicted as a typical perfectionist; well-behaved in class, calm, and hard-working, as opposed to Ramona's active imagination and unintentionally troublemaking personality. However, she is a bit of a snob, exaggerating the pain felt after Ramona tugged her curly hair in Ramona the Pest for attention. Also, she did copy Ramona's work. In the final book of the series, she refuses a slice of cake during Ramona's birthday celebration claiming that it is probably unhygienic and eating an apple instead, but soon afterward she confesses, in tears, her lifelong strive for perfection among adults, and her relationship with Ramona Quimby seems to improve afterward. In the same book, it is revealed that her parents tell Ramona to "be nice".
In Ramona and Beezus, Susan is portrayed by Sierra McCormick and seen as more of a bully than anywhere else in the series. She is portrayed as being full of herself and stuck-up, auditioning to star in television advertisements for a well-known brand of peanut butter as its princess mascot, donning a tiara at school, albeit whether or not she was selected for the part is unknown.