The undead and her useless Master

Many years ago, a girl was cursed after causing a great tragedy. She was cursed to live forever, but that's a good thing, right? After living through most of the traumatic moments in history, and experiencing many painful deaths, she realizes that her curse wasn't just petty dying words from those who hated her. One day, a strange elderly lady gives her a book that enables her to summon Satan, but when the book summons what seems to be a fraud. She comes up with a sinister plan of her own..