I think we just got a clue on who Ooki actually is, with the way she refers to other people as "common". At the very least, she seems pretty confident in her social or economic status, meaning she's either incredibly rich or incredibly skilled at manipulation because she's been doing it her whole life to coast around. Or both. As to why she's so physically capable, well, this is a series where sensing someone looking at boobs is an ACTUAL power so who knows how far the author might take it but I'll just assume she's trained and not some kind of Saiyan-Type alien.