Jennifer Ealey 
The Wizardess [EPUB ebook] 

As the confrontation between King Kosar and Prince Jarand looms, forest fire, subterfuge, clandestine troops and poison all threaten Prince Tarkyn and the woodfolk.
When the Wizardess of the Lost Forest comes to Tarkyn’s aid, she reveals a shocking secret that threatens their very future. Bolstered by her unparalleled power, Tarkyn and his followers desperately attempt to stave off a civil war.
But can Tarkyn find the strength to change the course of their realm, and save them all from the destructive, power-hungry rivals?