Mabel Longhetti is a fictional character from the novel "Mildred Pierce," written by James M. Cain. She is the daughter of the main character, Mildred Pierce, and plays a significant role in the story, which explores themes of ambition, family, and sacrifice during the Great Depression. In the narrative, Mabel is depicted as a complex character who struggles with her identity and relationships. Her interactions with her mother and sister, Veda Pierce, highlight the tensions within the family, ultimately shaping the dynamics of their lives and decisions throughout the novel.