Tangled question even if you don't have an alien mindset. If I were somehow put in a situation such that the only way I could come up with to save my wife from death or worse was by sacrificing a friend of hers . . . it would be tempting. I'd know ahead of time that she'd be really, really upset about it--heck, I wouldn't love her if she'd be OK with it. I'd be really unhappy about the idea of doing somebody in. But still, I love her, not the friend, and upset is better than dead. I probably wouldn't, but . . . I can understand the mindset of doing anything to save the one you love, it's not really alien to me.
If you take one of those horrible "people on the tracks" morality problems--if my wife was on one switch and three people I didn't know or didn't know that well were on the other and I had to decide which way that runaway train was going . . . uhm, sorry, three people.