If she likes historical fiction, I'd recommend The Agency series by YS Lee. It's about a 17-year-old girl in 1850s London who is a secret spy for an all-female spy agency. It's an excellent book with a strong female lead, with only a hint of romance. The author has a PhD in Victorian literature and culture, so not only is it engrossing, it's also fairly accurate (except for the all female spy agency part). It's targeted for grades 8-12 but I also really enjoyed it.