Charmfall (Dark Elite, Book 3) 1st edition

Protecting Chicago from the dark side of life can be an exhausting job, especially when you're in high school. So when the girls of St. Sophia's start gearing up for Sneak, their fall formal, Lily decides to take a break from fighting to get ready for the event. But when a Reaper unexpectedly crashes the party prep and Lily's firespell fails, she realizes that she has a much bigger problem than a full social calendar...