Joan is from Esther's hometown, goes to the same church, and is two years ahead of Esther in school. Joan is what Esther calls a "big wheel" — that is, she is president of her class, a physics major, and the college hockey champion. Joan is also a girl whom Buddy had dated before he takes Esther to the Yale prom. Buddy finds Joan to be a good sport, someone with whom he can do athletic things, and she doesn't have to be "pushed up hills."
As it turns out, Joan is very much the psychological double of Esther: they are both over-achievers; they are both unconventional young women. They both garner awards and succeed in their fields, and they both believe that they should try to become carbon copies of Mrs. Willard, the epitome of what a "successful wife" is in the 1950s. In addition, both girls attempt suicide, and both have woman doctors.
However, Joan is different from Esther. For one thing, she seems more impressionable and less critical of the influences around her. Joan loves Mrs. Willard, whereas Esther withholds her total admiration for anyone. Joan's field of study is physics, but after she has been in the psychiatric hospital, she wants to become a psychiatrist. She is in awe of Dr. Quinn, whom Esther describes as "a bright, shrewd, single lady," a person who gives Esther "the polar chills."
Joan is one of those athletic girls described in magazines of the 1950s as being "horsey," and Esther is shocked to find her friend in a lesbian embrace with another girl in the hospital. Esther, herself, is tall and gangly, but she is not "horsey" and, certainly, she is not the typical feminine woman of the 1950s.
Joan accompanies Esther to the hospital after Esther loses her virginity and can't stop the bleeding. After this experience, Joan returns to the mental hospital even though she had earlier been released; at that time, Esther was envious of Joan's "freedom" and of Joan's being "cured." Shortly after returning to the hospital, however, Joan leaves the grounds for the evening and never returns. She is found — hanging, in the woods. The reader never finds out what went wrong for Joan nor why she kills herself, whereas Esther, seemingly, recovers. Esther goes to Joan's funeral and repeats, "I am, I am, I am." Significantly, Joan, Esther's peer and competitor, is not.