Of course, that’s not so far removed from what actually happened, except there were no diaries. The Little House series was written when Laura Ingalls Wilder was in her 60s and 70s, although she had done some local journalism starting in her 40s. Her daughter, Rose, who lived with her, was a very successful author and journalist (ghostwriter, as well, and later Ayn Rand associate), and encouraged her mother to write a memoir of her pioneer childhood as a moneymaking venture. She edited the books, and arranged for their publication. She maybe went so far as actually to write them, too; lots of dispute about that. She had a huge hand in converting the original manuscript into a book for children at the suggestion of a publisher, and she simultaneously wrote some adult novels using the same materials.
Little House on the Prairie is the most artificial of the books. The Ingalls family settled in Indian Territory when Laura was 2 years old and left when she was 4; there’s little or no chance she actually remembered much about their time there. Laura and Rose substantially changed the chronology to make literary Laura older when the family lived there, even though that rendered the story of their settling and leaving completely senseless from a historical standpoint. As I understand it, very little about the book jibes with historical records even of the time the family actually lived there, other than the basic fact of a land rush by settlers who believed Indian land would soon be opened to homesteaders.
In other words, Little House on the Prairie is anything but a faithful personal recollection of Laura’s childhood. It’s a story Laura clearly wanted to tell, probably because it was likely to sell. Of course, there’s nothing wrong with that, but it does emphasize that she (and her daughter) was responsible for what story she chose, and how it was told, in 1931. not 1871.
(By the way, Wikipedia reports that Rose Wilder Lane spent a good deal of time in the 1940s as a columnist for an African-American newspaper in Pittsburgh, where she railed continuously against both racism and New Deal collectivism. It seems likely that Rose, at least, would have disagreed with “Ma’s” racism, although it may be equally likely that she thought the Native Americans were doomed by clinging to their primitive socialism.)