Watashi wo Henshin Sasetekureru Hazu no Mahoutsukai ga Mottokare datta Ken.

Kanae, an ordinary Japanese office worker, was reincarnated into another world. Thanks to her memories from her past life and her familiarity with fairy tales, she realizes that she's now living as Cinderella! All she has to do now is wait for her fairy godmother to come and free her from her life of toil so that she can meet her prince. Finally, on the day of the royal ball, just as she's doing laundry and contemplating when her fairy godmother will arrive, someone comes crashing down from the sky. To Kanae's surprise, this mystery person is none other than her fairy godmother... and her ex-boyfriend from her previous life! Unfortunately, though Kanae remembers breaking up with him due to his rude and prickly nature, she doesn't recall how she died. She can only assume that her former self never got her happy ending. What was the cause of her death in her previous life? Will she be able to find happiness as Cinderella in this life? What will become of Kanae and her ex? (Source: MangaPlaza)