How about they sacrifice the white woman because she's a stranger they have no emotional attachment to?
Um, I see your point. However, they didn't sacrifice her solely
because they had no emotional attachment to her. After all, they've been offering up their own women for who knows how long. And, presumably, the men do have some sort of fondness for their women. So the fact that the female outsider is just that, an outsider, doesn't preclude all other possible reasons for her little adventure with Kong, right?
Granted, at the very least, they figured they could postpone sacrificing another one of their own women by serving up the delicate-skinned, blonde stranger. Then again, it seems much more plausible that they
stop sacrificing their own dark women because they take one look at the white girl and think she's gotta be the tastiest treat they could offer Kong.
Besides, it stands to reason that they'd never have risked giving Kong a "below standard" entree. Not a good idea to anger a hungry monster. So they had to think that Fay was at least as "valuable" as their own women. On the other hand, it makes even more sense that they have a second bigger reason for selecting Fay: they think this gal, with her peaches-and-cream complexion, might be more irresistably precious than their own women, with their dark, mocha-ish complexions.
(i.e., "Wow, this girl's out-of-this-world strange. Gorgeous even. In fact, she kinda seems more special than all the other chicks we've got hanging 'round here. Hey, here's a thought--anyone think she might just make the big hairball happy enough to leave us alone forever? Golly, wouldn't that be super!?")