A bit of trivia I learned by visiting the Ingalls sites in DeSmet, SD in 2004: In real life her name was not Nellie Oleson, I forget what it was, but the publisher could not find her to get her to sign a release before By the Shore of Silver Lake was published. Laura Ingalls Wilder did not know her married name. So they invented the name Nellie Oleson for the person she had known in the 1880's.
Turns out she was tracked down long after her death, and her family said she knew it was her they were talking about but she would not come forward.
In real life her little brother Willie got killed.