I am confident more than a few church librarians have been asked to assist a parent whose daughter is an advanced reader, but not ready for the mature subjects that books at her reading level provide. We would appreciate any wisdom on this topic.
How about the Anne of Green Gables series, Little Women, Chronicles of Narnia, The Hobbit and Lord of the Rings trilogy? There is also a new graphic series for preteen girls by Angie Spady, The Desperate Diva Diaries: Catie Conrad from B&H publishers which she might enjoy. Don't think you can go wrong with Robin Jones Gunn's series for teens, Christy Miller and Sierra Jensen. Maybe James Herriot's All Creatures Great and Small and other titles?