This book is an excellent lower YA fantasy with hints of romance. My 5-star review is forthcoming.
The Witch Hunters have come for Brusenna, for she is the last. All the others have been captured by the Dark Witch. And without their magical songs to control nature, the world is dying.
Though young and untrained, Brusenna must succeed where every other Witch has failed. Find the Dark Witch. Fight her. Defeat her. If Brusenna fails, there will be nothing left to save—for the Witches, for mankind, or for the young Guardian who has committed his life to protecting hers.
Blurb and cover from Goodreads