When you say face-palming, do you literally mean she is taking her hand hitting herself against the face, or do you mean she is often resting her head in the palm of her hand, kind of supporting it wit her hand.

The two of these, two me, are a world of difference. Some people have a heck of a difficult time staying awake when seated and that may be the case. If she is actually doing the "face palm" when you're talking to her on the other hand, I think that is very disrespectful.