The true knight (The Warhorse of Esdragon # 3)

Titch has trained all his life in the ways of honor and of arms. Now he saddled his late father’s warhorse, belted on his heirloom sword, and set off to win his knighthood. Unfortunately, his first challenge pitted him against a formidable foe on a glossy black charger, and winning wasn’t in the cards for Titch – though he’d see the horse again . . .
Wren was an apprentice magician, a shape-changer and healer. She chanced upon the wounded warrior, ambushed and left to die. She took Titch in, nursed him back to health, then sent him on his way – though she’d see that youth again . ..
For a mad queen and an impossible quest would reunite Wren and Titch and the magical stallion Valadan. Together they would search out an enchanted swan, which Wren must somehow transform into a prince. Should she fail, she would pay with her life. The penalties would be higher yet should she succeed!
(from the back cover)