The question of Edie's antagonist is an interesting one. Within the story, there is no single character against whom she must strive consistently to prevail, nor is there one individual who plays the central role in the major conflict of the story. Loretta Bird annoys Edie and treats her with disrespect, Chris Watters inspires her romantic fantasies, Mrs. Pebbles gives her a job but doesn't treat her well, and Alice Kelling shows up as her competition with Chris, but not one of them unifies the story as Edie's protagonist; instead, each one plays a role--significant or insignificant--in Edie's journey toward maturity.
Edie's real antagonist, then, is her own inexperience because she is just becoming a young woman. Her youth and inexperience account for all of her struggles in the story. When she finally grows up, through suffering and disappointment, Edie finds real love, marries, and establishes her own home. In doing so, she leaves everyone behind who had played, as it turned out, minor roles in her life overall.