What if you're attracted to them in part or in whole because they're desperate to kill you, and by definition you can't get that vitamin from someone who isn't?
Well, it's not like I've ever had any difficulty getting people in the mood... okay, but, what if you're attracted to them in part or in whole because they're dangerous and defiant and desperate to kill you and you don't want to just suggest Sabina into the right headspace because a) that'd be play-acting (not that there's anything wrong with play-acting) and b) what if she successfully killed you because you didn't have Sabina on hand to keep the dangerous member of the rebellion from killing you?
No, none of this even gets at my real complaint. My real complaint is that people just aren't fungible goods. If I'm besotted with, take a random example, and this is a wild hypothetical here, you, I don't think "oh, but there's probably someone who's just as attractive." They aren't you. And I want you. If someone else is "equally attractive," that just means I want her too.