Read Return of the Female Knight manga
Elena, who spent her entire life as a cold-blooded female knight to avenge her family, ended up dying without claiming her revenge. When she opened her eyes she found that she went back into the past. By day she was a lady in a dress, and at night she carried a sword to change history and prevent her family’s destruction. “I want to marry you, Your Highness,” she said to the crown prince. She would do this to save her family.