The Fae King's Deadly Bride

Vesper, last dragon of Dragon Keep, orphaned by fae soldiers, enters King Rhyad's Bride Trials hiding a blade for his heart, trained by cousin Laros for revenge. She wins his admiration and falls in love, unable to kill him. Exposed as a dragon, she is named queen anyway. Laros attacks Rhyad, so she kills her cousin and confesses her mission. Fae law demands her death, so Rhyad kills his commander to save her. Told she costs him the crown, Vesper flees, leaving him to decide if he reclaims her.