Tempests of Truth by Melanie Cellier

Having finally rescued her friend, Delphine is left with a secret that could put all of Tartora at risk. Stranded on an island and with their relationship in tatters, Delphine and Nik are further than ever from finding and defeating Grey. But now they know the truth of his ability, they can’t let anything stand in the way of stopping him.
Delphine’s unique skills are their best tool for facing Grey, but they also make her a target. Nik wants to protect her, and Delphine’s heart wants to let him, but his status still stands between them. With fear and danger on every side, Delphine will need new levels of determination and courage to save both Tartora’s future and her own.

If you enjoy strong heroines, fantasy worlds, adventure, and clean romance, then try A Mage’s Apprentice, set in the same world as the completed Mage’s Influence series.