Who is Julia Lacey from The Favored Child and what is their importance?

Julia Lacey grew up believing she was the daughter of Harry Lacey, squire of Wideacre, and his wife Celia, and that Richard was her cousin. She greatly resembles Harry's sister, Beatrice. As is later revealed, Julia is actually the daughter of Harry and Beatrice. The man she knows as "cousin" Richard is actually her own brother, also the child of Harry and Beatrice. Julia has inherited Beatrice's love of the land and her dedication for Wideacre.