How Was I Supposed to Know the Heroine Would Turn Evil?!

(Genderbender + 1v1, with a protagonist who attracts everyone) Si Lanfeng, an upstanding young man who had never done anything wrong, never imagined that one day he would be sent to another world, just like in an anime. The method of transfer was brutally straightforward... And even more unbelievable, when he opened his eyes, he had gone from being a man built like a corn cob pipe to the petite, adorable Saint Cecilia. Well, turning into a girl after reincarnation is perfectly normal, right? Si Lanfeng, now Saint Cecilia, accepted her new identity with ease. But who could have guessed there would be a second challenge waiting for her? A blue-haired ditz who claimed to be the Goddess of Reincarnation appeared in her dream with a cheerful smile and delivered the most tragic news imaginable: she had landed in a story about the true and false saintesses, and she had already offended the real Saintess! This is bad! Is there still time to start over and make things right? Cecilia tries to save her own life. She doesn't want to die young, after all. So all she has to do is be a little nicer to the heroine... right? Wait... Wasn't the heroine I raised supposed to be a sunny, cheerful little sweetheart? How did things turn out like this? I hate you, you blue-haired idiot of a goddess!!!