She forms a bond with the dragon, who has been unaware of the periodic human sacrifices committed in his name. They have some adventures, she gets a dryad servant. They interfere with a neighboring country's civil war, he becomes king of that country. He sends her back as an emissary, to her old kingdom despite her protests, thinking it's good for her. Her dad thinks she's crazy, her sister shows up to flaunt her fiancee, the prince is deeply worried by the implications of her return, the king decides she's a coward who fucked up the human sacrifice, then the dragon shows up, turns out he had been sense sharing with her, he is pissed beyond belief and declares himself the new king, while showing off how impossible it is for him to be harmed or opposed. Sister tries to seduce the dragon and turn it into MC manipulating him, MC loudly protests that she's just a servant, not a love interest, sister gets shittier, dragon just starts choking her to death.
MC stops him just short of casual murder, and he flies back to his volcano, wondering just what exactly is wrong with humans.