"Dragons and Dreamsellers" by Krista Joy.
Letisha Tate has a problem keeping time. Now her problems multiply with a sudden change in her summer holiday plans. On short notice, and much to her discontent, her parents send Letisha to stay with an old family friend. Mr. Tempus appears at first glance to be a watchmaker with an odd little shop. And far, far odder customers, something Letisha comes to appreciate when a dragon named Sheridan appears at the back door inquiring about the repairs on his watch. When Mr. Tempus is kidnapped, it is up to Letisha and her new friends to rescue him -- only not everything is quite as it seems.