The Bastard Prince (Dragonspeaker Chronicles Book 1). Dragonspeaker Chronicles, #1

She has a dragon, and she's not afraid to use it. Nellie Dreessen is a kitchen maid in the palace of Regent Bernard of Saardam. She has worked for two kings and two regents, has seen two royal families murdered through magic, has seen ghosts and demons, and kept her head down like a good girl. On her fiftieth birthday, she receives her late father's diary, which describes a magical item that is so evil, it needs to be kept in the church crypt: a box that contains dragon.
Problem is, someone has stolen the box. Regent Bernard holds a banquet for his eldest son's sixteenth birthday. Distinguished guests come from far and wide. Because she knows what the box looks like, Nellie discovers it in a nobleman's luggage. Removing the box from a thief's room is not stealing, right? Not if you intend to return it to the rightful owner: the church. But someone poisons the nobleman, and everyone in the kitchen is a suspect.
Nellie's friend in the church advises Nellie to flee with the dragon box. The Regent is on a mission to stamp out magic, and Nellie plans to do what she does best: keep her head down and hide. Problem is, the dragon has other ideas.