Echoes of Understorey / Thoraiya Dyer.

In the quest fantasy Echoes of Understorey, part of Thoraiya Dyer's extraordinary Titan's Forest series, trees loom large as skyscrapers, mortals can be reborn as gods, and a young woman finds herself part of an adventure that is destined to become legend ... Great deeds are expected of Imeris. She has trained endlessly to become an extraordinary fighter. Yet she wants more than to compete against the glories of her divine sister and the charms of her courtesan brother. Imeris thought she could prove her worth during a mission to kill a body-snatching sorceress, but fails disastrously. With death on her conscience and in hiding from her peers, Imeris is determined to find a way to redeem herself. What she doesn't expect is to be recruited in a Hunt for the Ages, chasing a terrifying, magical beast that will take all her skills to stop.