Ah, my apologies for the mix up - Dante477 seems to have the right of it.
However, an argument for inference can be made on Bris' behalf: I'm not sure where exactly - might've been with the human traders on a quest for Vehlis - but at some point outside of the camp it get's mentioned that a Dufuor / Dufour daughter was killed in the area, so it could be said that Sabia's 'death', even without her name specifically being mentioned, is not uncommon knowledge.
Bris puts things together - time of arrival, her demeanour, hair (though not necessarily) - and her identity is uncovered. Made easier at any point by asking a person who would know, 'what was this noble's first name?'
Though I doubt the head cat girl has many days off to pop into town, although she did lead the caravans, which could very feasibly be trading with Grog ok Dar.
Mind you this is all speculation and conjecture, and even as I write it it does sound a little far-fetched.
But yeah: although I have an older version that funks out due to image conflicts at that point, it is not made clear how Bris comes about this vital piece of information.
Another possibility: working in the tents - much ado has been made about them being a source of information - an orc could have mentioned the original raid- oh wait no, they didn't know who she was either. Never mind!
(Actually come to think of it, I wonder what in the capital or thereabouts, was being said about it? Her mother and sister were behind the attack, but surely someone wondered about their daughter/sister and potential war hero being killed off by orcs/ went walkabout near orcs and the lack of punitive measures being taken - something I quite easily imagine the ladies would do. Crap, now I've outhought meself: either one of them could say that she was on a secret mission or an extent patrol. Or anything. I'm gonna stop writing now and press send.)