I Was Called Useless for Not Using Spirit Magic and Had My Engagement Broken. So I Chose Exile Over Becoming My Stepsister's Slave

Eva, the eldest daughter of the Duchesse de Crozic, is an incapacitated person who cannot use spirit magic. Her biological father and mother died when she was young, and she has been treated like a servant by those around her. When her fiancé, the Dauphin Risley, is found to be having an affair with her sister-in-law, Marti, the two conspire to force Eva into exile or to become her sister-in-law's maid of honor. Eva chooses to be free rather than stay in the country, and leaves the country for the neighboring kingdom of Foresti with her servant Alain and others..!