Onyx and Ivory by Mindee Arnett 

They call her Traitor Kate. It’s a title Kate Brighton inherited from her father after he tried to assassinate the high king years ago. Now Kate lives as an outcast, clinging to the fringes of society as a member of the Relay, the imperial courier service. Only those most skilled in riding and bow hunting ride for the Relay; and only the fastest survive, for when dark falls, the nightdrakes—deadly flightless dragons—come out to hunt. Fortunately, Kate has a secret edge: she is a wilder, born with magic that allows her to influence the minds of animals. But it’s this magic that she needs to keep hidden, as being a wilder is forbidden… Read more.