ACTUALLY jester, that sounds interesting. If Nalia is not there with you while you're in the keep and you DO kill the aunt, she can't possibly know it was YOU who killed her, unless you admit it, or one of the other NPCs says so. It would be good manipulation of her then, for an evil alligned person, but also you could say something that would trip you up, for example if you said "Sorry Nalia, both your aunt and your father were killed by the trolls, I have slain their leader however." and Nalia, being the naive person that she is, would not notice that you shouldn't know who her aunt was at first, but after a few days she might come to a realisation - that'd be nice, but complicated.
Something like "How could you know who my aunt was?" and if the PC has high charisma then maybe he could convince her by saying something like "One of the servants informed me, just before he was attacked by one of the trolls in the keep." etc etc.
Course you could say you just couldn't find her.
Good suggestion? Maybe something for after the mod is initially released, it'd be a good way for an evil character to manipulate her, as I said earlier, what with all her family dead now, and her very vulnerable, naive and open to comfort - if you see what I mean. Maybe this is too much, really, for the scope of this mod?