After watching the video, I think the problem she had in resizing is not because it isn't intuitive, but because it required more delicate movement. The same reason it would be harder for her to twist a screw driver than to hit a hammer.
Having played with one of these, and knowing how it works under the hood, it's more likely that she just didn't have the technique right. Surface prefers you use single fingertips as points of control; Isobel was using her entire hand.
