Ah, I understand. Thank you! Though if if you wouldn’t mind another answer, please... why Mr./Mister Bushido? Does she not call him Bushido-san or the like?
It’s from her Baroque Works speech pattern! All their code names are specifically written to be pronounced as ‘Miss’ (ミス/misu) or ‘Mister’ (ミスター/misutaa) in Japanese- Mister Seven, Miss Wednesday, etc. And when Vivi first calls Zoro ‘Mister Bushido,’ it’s at Whiskey Peak while she’s still in her BW persona, so that’s what she uses, and then it just sticks after that.
Which reminds of another question over always had:
So Vivi ends up referring to Chopper as Tony-kun if I recall, from watching the anime. Any explanation on that? I thought it was always pretty special since I don't think Kureha even uses Tony.

