I agree it can be weird OKing some horrific things and not others, but we do also tend to have some fairly set social conventions about these things. Some of those are silly (graphic violence OK, me shirtless = won't someone think of the children?), but we can modulate a bit between the two and come up with something reasonable as a baseline. And then RP that goes beyond the baseline can be restricted (whether that means it needs a warning or just shouldn't happen is up to the staff).
Her game sounds like it has a pretty obvious set of inspirations, and Black Sails is among them. It has both a fair bit of graphic violence (including some of the nasty realistic consequences like amputation with shit medicine) and sex, and even sexual violence (see Max), albeit in the last obviously more is implied than shown. From that you can pretty easily find the common (sex, violence) that people should be OK with to even step foot on the game, but also probably the high end where a warning might apply (extreme gore, actual porn, rape, etc). Doesn't seem crazy.