In Mon-Musu Quest!, this version of Alipheese Fateburn XVI first shows up in Part 3 after Promestein makes a sealing device to replicate the Six Ancestors Great Seal that was used on Tamamo (Mon-Musu Quest!).
In Mon-Musu Quest: Paradox, Alipheese Fateburn XVI is already in this form when you first encounter her. She can be unsealed later to her original adult self.