The Beast Player by Nahoko Uehashi

Elin's family has an important responsibility: caring for the fearsome water serpents that form the core of their kingdom's army. So when some of the beasts mysteriously die, Elin's mother is sentenced to death as punishment. With her last breath she manages to send her daughter to safety. Alone, far from home, Elin soon discovers that she can talk to both the terrifying water serpents and the majestic flying beasts that guard her queen. This skill gives her great powers, but it also involves her in deadly plots that could cost her life. Can she save herself and prevent her beloved beasts from being used as tools of war? Or is there no way of escaping the terrible battles to come?