That older account is friends with Iron Mouse (maybe), but has seemingly no other vtuber account friends. But aint much you can do with privated accounts. Don't know why she'd have two Demon Dice accounts instead of one Demon Dice account and one Mori account.
E: Also, I don't know her dox as im not a holochad, but the second account has location set to Texas, is she a Texan? That'd be at least some circumstantial evidence that the older account is her.
E:E:
View attachment 27643
Shiina next game is Star Wars, I'm looking forward to her battle with frogs