The Reincarnated Saintess Chooses Death for Her Love

[This is much worse than the original story...!!] A Girl, who died together with her family in an accident, was then reincarnated as the main character, saintess Cecilia, inside the novel she loved. In the original story of the novel, her twin sister, Rebecca, had turned into a villainess and killed their father because of her envy. The saintess is determined to change the course of the story because she doesn't want to lose her family once again. However the story turned into the worst case scenario and she was killed by Rebecca instead...! Upon dying, a mysterious power sent Cecilia back to the past where she hasn't been chosen as the saintess yet. Now she is forced to make a certain choice to change the course of the story.