In Joyce Carol Oates' short story "Where Are You Going, Where Have You Been?", Joyce serves as a foil for the character of Connie.  A 'foil' is a literary term for a character that the author uses as contrast against another character; in this particular short story, Oates uses the character of June to reveal more about Connie's personality and flaws.  June is the ultimate 'good girl' and everything that Connie rebels against:

"Connie had to hear her praised all the time by her mother and her mother's sisters. June did this, June did that, she saved money and helped clean the house and cookedand Connie couldn't do a thing, her mind was all filled with trashy daydreams."

Connie's sense of inadequacy when compared to June causes her to act out.  She is desperate to reinvent herself as to avoid becoming her big sister.  Oates' uses June in "Where Are You Going, Where Have You Been" to provide a contrasting portrayal of feminity against Connie's wild, reckless behavior.