“Nothing at All, A Dragon Tale” by Julia Pferdehirt.

Ona doesn't have any particular talent, not like her brother, the swiftest runner, or her sister, the storyteller. In fact, Ona means "nothing at all." But when the dragon from the distant mountains threatens to burn their village, it is Ona that is clever enough and brave enough to riddle the dragon, sending him back to the high mountains and earning herself the name Kima Reetana-"Brave One, Who Riddles with Dragons."