Some time ago I played a Co8 version of TOEE that included the skeleton of what I refer to as "The evil bitch" quest(s). You know, some kind of utterly evil nobility hanging out in Nulb, abusing the whores and generally doing a lot of evil-type revelry. She has henchmen here and there as well, iirc everyone is supposed to be terrified of her. Did that ever get completed, and did it make it into any revisions of the modpack? I thought it was kinda neat, although not fully fleshed out.
That was the short-lived prequel to The Slavers. (I take it you haven't done Verbobonc yet?) I was kind of partial to that too, but we've opted in favor of generally not interfering with the vanilla story with the NC. It only appeared in that one instance. Someday I'd like to have a discussion on the merits of 'adult' themed (and by that I mean rated R, not rated X) content like that.
I thought it might be her, but I didn't remember enough of her backstory or look. Hrrrm, well the slavers is one of the best flavor/personality moments of the whole game, imo. So even more backstory would be awesome, but then again, maybe it wouldn't. Mystery isn't a bad thing. I don't think you have to really get into adult themes too far if you convey the message the right way. Just overtones: she's abusing the whores in unpleasant ways. The end. But if that's your R, then yes, leave it in it has impact.