Great Falls Rogue by Alex Lidell

At the stroke of midnight, anything can happen.
Lera is walking a dangerous tightrope. By night, she takes off her veil to hunt the dark creatures leaking into the mortal world. By morning, she is Leralynn of Osprey again, failing her classes and dodging Deputy Headmaster River’s keen scrutiny.

River is watching Leralynn like a hawk. A painful distraction, since the mouthy cadet stirs his soul—and other parts of him—with a mere glance. Which doesn’t matter. Lera is a student and River will ensure she toes the line, or else.

As Ostera approaches, the night when magic is most potent, River is on high alert for any threat to the academy’s reputation. But he hasn’t prepared for a threat to his heart.
It is the grand Ostera Ball, and the clock races toward midnight…