I watched the entire interview with the sound off. She looked that sad in MOST of it. See for yourselves.
The weather's changing and they have kids in school, could be a cold or lack of sleep? Or, like you said, sad or...?
Maybe she's trying to tone down her looks. I think she's a beautiful woman, but being that attractive can get in the way if you want people to take you seriously.
Regardless, her analysis was very good and she gave us plenty of teasers.