Given my experiences with rewriting most of the game's dialogue, I'm gonna say Relm. This is mostly because I feel that everyone else was given adequate time (Umaro and Gogo don't count, Mog is intended to be a blatant corporate mascot insertion, and Gau is... well, Gau) and I'd enjoy more opportunities to make her be vulgar.
"You don't have to be a vampire to die like one... b*t*h." -Simon Belmont