Level Up by Slaying Monsters, Become the Demon Queen

The man she loved saw her as a pawn. She wanted to stay out of trouble, never imagining she was such a catch. After completing a mission, she was suddenly dragged into another world by a Demon God. With her cheat-like abilities, she battled monsters and leveled up all the way to becoming a Demon King. Then one day, the Demon God announced that she was his Demon Consort. What the heck? How could that be? Their relationship was clearly nothing but using each other.