Here are some potential antagonists:
* Catherine's anxieties and insecurities: These internal struggles are a major obstacle for Catherine. Her fear of rules and her desire for control create conflict both within herself and with others.
* The "rules" themselves: The book explores the suffocating nature of rigid rules and how they can stifle growth and freedom. This concept could be seen as an antagonist in its own right.
* Catherine's family dynamics: Her parents' divorce and the pressure to conform to their expectations create conflict and tension.
* The "perfect" image Catherine strives for: Her desire to be the "good girl" and her fear of disappointing her parents fuels much of the conflict.
* Catherine's lack of understanding: Her limited ability to grasp the emotions of others leads to misunderstandings and hurt feelings, creating challenges for her relationships.
Ultimately, "Rules" is more about the internal struggle of a character than a clear-cut battle against an external villain. The story explores the complexities of navigating social and emotional rules, making the protagonist's own internal conflicts the driving force of the narrative.