On one hand, it'd make sense for Sakuya to have turned her, since she's into that type of girl. But if Aria is as old as sometimes is implied it's kinda unlikely that she'd be even older. So, yeah, I think it's a bit like her calling her manservant a burglar in the first chapter; some dismissive "oh, that's the role they currently play..." thing, no "real" relationship.
Anyway, agreed, great finale to the chapter!