While the speaker is anonymous (e.g. "might be me"), I'd like to think that it's Sanae. 🤨 'Cause I doubt Suwako would even call herself granny to, well, anybody but her.

Hmm... if Suwako counts as Sanae's granny, and we can assume that Reimu's granny is Yukari... who would be Marisa's granny? 🤔 Ah! Patchou-