Help me find this supernatural/fantasy book about the daughter of a rich criminal

Question

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.

Answer 1

This is Seven Black Diamonds by Melissa Marr.

Lilywhite Abernathy is a criminal. Her father’s “unconventional” business has meant a life of tightly held secrets, concealed weaponry, and a strict code. But Lily’s crime isn’t being the daughter of a powerful mob boss. Her guilt lies in the other half of her DNA—the part that can coax ancient rumors from stones and summon fire with a thought. Lily is part fae, which is a crime in her world.

From the time before she was born, a war has been raging between humanity and fae. The Queen of Blood and Rage, ruler of both the Seelie and Unseelie courts, wants to avenge the tragic death of her heir—a death that was the fault of reckless humans.

Lily’s father has shielded her from the repercussions of her ancestry…until she is sent to the prestigious St. Columba’s school, straight into the arms of the Black Diamonds.