I don't think body positivity = be fat, it's about accepting that your body doesn't define you, and that you should have the right to feel beautiful at any size. She probably physically feels better slimmer--I know I do. And just because she lost weight doesn't mean she's a normal sized model. She's still a thick girl. See pics.
I don't mean to get into an internet fight, I just try to stay aware of our role as FAs in this community. It's just as bad to get on someone's case for losing weight as it is to get on someone's case for gaining weight. We're not in the right just because we have a preference for women leading the body positivity movement. I think using the body positivity movement as a front for your disappointment with someone's transformation is wrong.
I'm open to conversation BTW, again I don't mean to fight about this, and recognize I could be totally wrong. I just want to make sure we're being careful and not dismissing someone's role in a really important movement because they're not as fat as they used to be. That's as bad for society as fat shaming.