I found another anime doppelganger for Celestina other than Yu Mei Ren from FGO: Sakuya Kaguya from an anime called Shining Blade. I know nothing about it, but now I can collect more waifu merchandise.

Update: the anime is called "Shining Hearts" and the character looks different in the show, dressed like a pirate. The version I thought looked like Celestina was a "professor variant" which was made as a figurine but has nothing to do with the show or game. Disappointing.

@Tfmonkey Sumireko Sanshokuin from Anime Oresuki is a Doppelgänger for Celestina