Scent of Magic by Maria V. Snyder
As the last Healer in the Fifteen Realms, Avery of Kazan is in a unique position: in the minds of her friends and foes alike, she no longer exists. Despite her need to prevent the megalomanical King Tohon from winning control of the Realms, Avery is also determined to find her sister and repair their estrangement. And she must do it alone, as Kerrick, her partner and sole confident, returns to Alga to summon his country into battle.
Though she should be in hiding, Avery will do whatever she can to support Tohon’s opponents. Including infiltrating a holy army, evading magic sniffers, teaching forest skills to soldiers and figuring out how to stop Tohon’s most horrible creations yet; an army of the walking dead—human and animal alike and nearly impossible to defeat.
War is coming and Avery is alone. Unless she figures out how to do the impossible ... again.
I think Maria V. Snyder's books are really good, and I can't wait to get my hands on the next book in her Touch of Power series!