Give an example of a character who serves as both foe and friend to David

Consider Sophie. Early in the novel, David discovers that she has six toes on each foot, thus making her a mutant in their society. Nonetheless, Sophie and David become friends and share a sort of childhood love between them. She is portrayed as a strong, independent, and curious little girl. As an adult living in the Fringes, she is portrayed as resourceful and clever. Martie and John Wender are her parents. Later in the novel Sophie must protect herself from at least what David represents.