In the Little House book series, Laura gives the impression to readers that Nellie Oleson is slightly older, which matches the bully person she has in the series. And because school was taught in a single room, unlike school today, it wasn’t apparent just how much older Nellie was than Laura.
Nellie Oleson was actually a combined character from three different girls Laura knew growing up, and she changed the name because Nellie was not shown as a nice person. Nellie Owens was one of the primary “Nellies” in the book, as it was Nellie whom lived in Walnut Grove, had a brother named Willie, and whose parents owned the mercantile in town.
The real Nellie Owens was actually two years younger than Laura Ingalls. Nellie Owens was both August 2, 1869 while Laura was born in 1867.
Genevieve Masters, one of the other Nellies, was born in 1867 and was the same age as Laura.
The last Nellie, Stella Gilbert, was born in 1864, so she was the oldest of all the girls and was three years older than Laura.