Kristi is Catherine's new neighbor. Like Catherine, she is twelve years old. Kristi's arrival is an opportunity for Catherine to make a new friend. At first glance, Catherine describes Kristi as looking "just right" and immediately feels that she will be popular in ways that Catherine is not.
While Catherine and Kristi have few similar interests, they become fast friends. Since Kristi is viewed as someone who is cool, their friendship serves as confirmation for Catherine that she can fit in with the social groups she often feels alienated from. Catherine's need for Kristi's approval is an important aspect of the story. Kristi represents Catherine's desire and ability to be accepted by "normal" children. However, her character serves various purposes as the story unfolds.
Kristi's role illustrates how first impressions cannot reveal the personal struggles a person might be facing. While she is viewed as "normal" and popular, Kristi is coping with the divorce of her parents. Like Catherine, Kristi struggles with a feeling of being divided within herself and her environment, even expressing that she would like for her parents to get back together.
Kristi is an important character because her role helps further the idea that "normal" is just a stereotype and not a word that should define a person's value.