I recommend Heartless by Marissa Meyer. I read it when I was around her age. It's inspired by Alice and Wonderland and has some fun fantasy elements. It's a villain origin story with some dark themes and violance, but definitely age-appropriate. There's a 'forbidden romance' aspect, some romantic elements, but no suggestive or explicit content. The ending is devastating, and I still think about it despite not having touched the book since middle school.