Oreo

"Mirror mirror on the wall, who is the prettiest dragon of all?"

"Beauty is in the eye of the beholder, so the "prettiest" would be an opinion, not a concrete fact."

"... You couldn't just play along, could you?"

Nicknamed for her colors and love of the cookies, her true name is unknown to all but her immediate family. It was her own brother who started calling her that as a sort of tease, but it just stuck. He'd introduce her as her nickname as part of the joke, but some took it seriously and more started calling her that. She got so used to the nickname that it started feeling more like her name than her real one. She even got to the point where she'd introduce herself as such. So her true name was forgotten and thus she became Oreo.

Oreo is a rogue and she used to accompany her brother on jobs. Although ever since he joined the guard, she's had to go solo. At first, she just continued doing what they always used to do. However, her own brother caught her stealing a valuable item and had to arrest her. Miyako hated having to do that to her, but he didn't have much of a choice.

So while he had the chance, he took the opportunity to talk to her and try to reform her. He offered her a job with the guard, but she refused. At first, she was just saying no because she was still mad at him for leaving her and also arresting her. However, even when she considered his offer, she didn't want it. She just didn't want to be a guard. She wasn't the warrior type. She liked being a rogue.

So Miyako offered her another deal. She could continue being a rogue, but be more like a spy for the guard. She would get inside information on criminals while undercover and report back to him. Then he and the others could arrest them. It would be a risky job, but she didn't have a lot of options. Oreo liked the idea, so she accepted, and she's been a spy ever since.