Shifter and Shadow — Sharon Shinn

Kirra Danalustrous is the daughter of a manlord, a celebrated beauty--and a shapeshifter with magic in her veins. After a disastrous affair with a married man, she has fled to the edge of the kingdom, to a small fishing village that has become a refuge for children dying from the invariably fatal red-horse fever. Yet Kirra has discovered a radical cure. She can transform the patients into animals who can take a medicine that's poisonous to humans. But so many people in Gillengaria fear and distrust magic. How many parents will allow Kirra to save their children? And if Kirra saves enough of them, will she be able to heal her own broken heart?--Provided by publisher.