This is not really a fair question because Julie is still technically a child throughout the entire book. In fact, Julie is forced into an arranged marriage once she turns thirteen and experiences all of her adventures with the wolves during this same year. However, because of the way your question is worded, I assume you mean Julie's very early childhood. Therefore, Julie spends most of her childhood in or near the Alaskan village of Mekoryuk.
Before Julie is four years old, she has both of her parents to care for her. Her father has a "regular" job in Mekoryuk village, and the family is fairly happy. After Julie turns four, her mother dies. This changes everything. In his grief, Julie's father, Kapugen, abandons all of their material goods and moves them to a "seal camp" near Mekoryuk in a "little house of driftwood, not far from the beach." It is here, near Mekoryuk at the seal camp that Julie's life is "infinitely good" because she is learning the "old ways" of the Eskimos in harmony with nature.
Julie's idyllic life with her father is cut short when Aunt Martha appears. Martha complains that Julie should be in school. Therefore, Julie is taken back into the village of Mekoryuk to live with her aunt. Although Julie enjoys school, she is unhappy with the care of her stern Aunt Martha. Therefore, when the opportunity arises to escape that situation through an arranged marriage (when Julie turns thirteen), Julie feels compelled to choose that route.