I read this novel in 2018 and back then it was ongoing. I remember that the title only has one word. MC(girl) transmigrated into the body of a girl who's madly in love with (?7th) or 9th prince and died by falling off a horse? She was a useless daughter and her younger sister was being known for having more talent? That said younger sister tried to kill her but later became super docile and close to her, I believe. I remember that she had a knight but he ignored her and almost let her die. But later, he begged MC to let him guard her and MC agreed? I remember not knowing who the ML is since the story was mainly focused on MC. She had magic talent after transmigrated and she also practised martial arts from her guard. I kinda forgot what was going on when I stopped reading it. But MC was quite close to her mother.
As far as I remember the MC died by falling off a horse. She has a power of light I think. She can cleansed a bad energy. The ML is a knight of a temple and became her bodyguard. I don’t remember of about a sister. I think there’s a scene about a desert. I also think there’s a scene where the MC heal a whole town/city using her power.