Bet 10 bucks on 2) Villain.
Is it even the type of story where there's an antagonist? We're 9 chapters in at this point after all and so far it's basically slice-of-unlife ...
So I'll pick 4) future member of her vampire harem.
5) Masochistic friend of Aria's. She used a shipping container to travel across international borders, spending nearly a month cooped up in an unventilated and cold box. Chances are she likes being on the receiving end of bondage and choking play, and playing up the necrophiliac aspect of the vampire legend.