I thought its western fantasy because all the characters have English names and the title has only one word. MC got transmigrated into eldest daughter of some duke or sth. Her body owner used to be a waste and chased the 7th or 9th prince of the country. Her body owner died from a fall from the horse or carriage. Her knight ignored her despite being her knight and she gave him a harsh lesson for it. The knight feels like the male lead but I'm not sure. She also has a magic genius younger sister who used to hate her a lot but later they got along.