Hush Now, Saintess!

She wakes up inside a chaotic novel in the body of Roella, a fake saintess destined to die young. After the initial shock, she makes a survival plan. When the real saintess appears, she will simply step aside and admit she must have been the fake all along. Just when she feels relieved about her perfect plan, a system window suddenly appears with a mission. It forces her to reform even though she is supposed to be a villain. She must improve her reputation and any swearing will be automatically filtered. If she fails, she will die within six months after the real saintess appears. If she succeeds, she will survive. The system asks if she accepts the mission.