I agree with the posts upthread saying we have lost sight of what a healthy weight really is. I live abroad and I am always shocked when I go back to the UK and see the sheer number of overweight people of all ages. It's not like that at all where I live.
I also agree that the DoC looks slim, slender, willowy, athletic (she is a keen sportswoman - well, she used to be - so I imagine her figure is toned due to years of doing exercise). I wonder sometimes if photos of her aren't photoshopped to make her legs or waist or whatever to look thinner than it really is.
Even so, I think it's awful to say she's horribly thin. There must be some really envious people out there.