As I pointed out over at the awful forums: if Mia and Tess had been worgen, they'd have gotten fuzzy under stress. And they were on quite a bit of stress on the trip from Gilneas to Teldrassil.
That's a deliberate understatement, for the record. Considering that they're nowhere to be found in-game, many a sigh of relief was breathed when they were still alive at the end of "Lord of His Pack." (But cue lots of jokes about Tess going out and deliberately getting herself cursed as an act of rebellion—or, alternately, in order to be more like Daddy.)