Iron Crowned by Richelle Mead.

This is the third in the Dark Swan series. Eugenie is in the middle of a war with the ruler of the Rowan Land, after having Katrice's son killed for kidnapping and raping her. Her lover and ally, King Dorian of the Oak Land, urges her to attempt a quest to find the Iron Crown which, according to prophecy, will give the one who possesses it the ability to end the war quickly. So Eugenie sets off with her former lover, the half-kitsune Kiyo, to win the crown and end the war.

After she acquires the crown, she finds out that Dorian has not been entirely truthful with her, and so she renounces her alliance and relationship with him, and rekindles her relationship (to put it very delicately) with Kiyo once more. When the united front she has presented with Dorian against Katrice falls, eventually Eugenie is forced to take drastic steps to end the war, doing the things she swore she didn't want to do.

You know, men are often accused of thinking with their gonads, but this female character of Mead's is worse than most men. I wonder if Mead is trying to surpass Laurell K. Hamilton's Anita Blake's record for total number of wild sex scenes in an urban fantasy novel. If she's merely going for emotionally conflicted heroine, she's not letting Eugenie remain in any particular emotional state long enough to actually fully realize the conflict. I have to agree with her stepfather, Roland, in my utter disapproval of most everything she's done, even with the best intentions, throughout the series.

Ah well, perhaps redemption is on the way in the next installment.