Final answer:
Junior's sister Mary occupies her time in Montana by attempting to write romance novels in 'The Absolutely True Diary of a Part-Time Indian', facing new life challenges.
Step-by-step explanation:
The story referenced does not provide details about Junior's sister Mary and her life in Montana, as it seems there might be some confusion with the text from "The Absolutely True Diary of a Part-Time Indian" by Sherman Alexie. In that novel, Mary escapes the Spokane reservation to pursue her dreams, one of which includes writing romance novels. She spends her time in Montana living in her in-laws' basement, attempting to write her novels, while dealing with the challenges of her new life.
Mary's experiences highlight themes of hope, escapism, and the struggles of indigenous people. Alexie's narrative often delves into how the characters cope with the realities of their lives and aspirations, and in Mary's case, her time occupies a mix of optimism and the confronting of new challenges.