Inferno - Destroyers Series, #2

Janelle is about to learn that the world is more dangerous than she ever thought... Two months after learning of her Tempest nature, 16-year-old Janelle is overdue for a vacation. Still grappling with her identity and past deeds, she hopes her vacation in Hawaii with Gareth will be the closest thing to normal she can get. Kenna, a bullied sophomore from Hilo, has never fit in, and her parents are as emotionally absent as pet rocks.
But her life quickly heats up when strange things happen. She becomes immune to fire, and the volcano seems to react to her presence. And, it turns out, her parents aren't really her parents, and her mother wants her back. So, when Kenna goes missing and Kenna's real mother believes that Janelle is the prime suspect, Gareth's life hangs by a thread. Janelle must find Kenna at all costs and solve the mystery behind Kenna's disappearance. If she doesn't, Kenna's secret could mean the end of civilization.
And Janelle won't let anyone else die, even if she has to sacrifice everything.