@kenx fair, but in Sumo's defense he's shown her every possible consideration and he's the -one- guy pursuing her who doesn't simply pay his way into her panties or rape/threaten to rape/threaten to enslave (looking at you crimson chump) her. maybe she's hypervigilant and worried that Sumo's holding back his particular dark side, but even then the evil you know would still be better than rolling the dice every night that your next john won't give you a disease, leave you pregnant or injure you or worse. even with the relative safety of a brothel (as opposed to a street corner), if she's rational enough to know she has no other cards to play just because she's a woman, Sumo would at least offer temporary relief.
then again, maybe forming that kind of commitment to her would mean giving up on going back to her own world and maybe that's why she'd rather make her way doing something she could walk away from if a portal home ever came up.