I think its a supernatural kind of book or fantasy. It's about this girl who is rich because her dad is a big criminal. She also has powers. The dad protects her from the outside world, even makes her homeschooled. Anyways the girl starts school, where rich people go to school in. She meets her favorite singer at her birthday party and finds out he goes to her school. She befriends this girl with red hair who is I think a model and her friends. The singer boy is included too. Long story short she is the last guardian they were waiting for.
And in this other world, there is a Seelie court and Unseelie court where the girl's grandparents rule (she finds out later in the book) separately. Anyway, the grandparents have a princess which is ugly?? But since their other daughter (the girl's mom) died, she is supposed to rule both courts. The half-brothers from the Seelie court don't want this to happen so they give her a hard time.