Why was dori mad at susan in the book Stargirl?

In "Stargirl" by Jerry Spinelli, Dori is upset with Susan because she feels that Susan, who has transformed into the more conventional "Susan" from her unique persona as Stargirl, is abandoning her true self. Dori values authenticity and is frustrated that Susan is conforming to fit in with the popular crowd. This conflict highlights the themes of individuality versus conformity present in the story.