As commenters mentioned below, the photo is rather terrible so it is hard to really judge how she looks due to lighting/tan/photoshop and the composition in general. But if the whole body positivity/HAES ideology is that one cannot judge another's health by size alone, than no matter how skinny she is, commenting that she looks "sickly and unhealthy" and needs to eat more because she is "deprived" is as you stated, extremely hypocritcal. And lord knows one would be flamed if they left similiar comments on a fat person's photo.  If commenting on the health of a fat person is "fatphobic" and bullying, than so is this. If hams are going to have stupid principles at least be consistent with them.