Look at the shadows along the sides of her belly. They're too widely spaced to be protruding muscle so it's got to be fat. As others have said, the rest is squashed into her tights which compress and hide the fat. You can still tell it's there as there is a rounded shadow under her belly, over her pubic area, that can't be explained purely by the fact that the fabric is thicker in that section. She's hiding behind her hair so I can't see her arms but even the small section of her chest that is showing should have the visibly protruding ends of her collarbones visible as little bumps. They're not there which means they're covered by fat. She's also changed her pose between the two pictures, standing legs apart in the second one to give the illusion of a thigh gap. Where the darker section (the constricting "control panel" of her tights) ends her inner thighs bulge out.  It's pretty obvious that if she adopted the same pose as the before picture, her thighs would still be touching each other. The change in pose also masks her arms as much as her hair does. If you look you'll see that they're pulled slightly back behind her body which again gives the illusion that they're much slimmer because you can't see part of them, especially as her forearms are raised which messes with your brain and creates a forced perspective. Pulling a face and having her mouth open like that elongates her jawline, instantly creating a slimmer facial outline (try it in a mirror!) as well as drawing in the cheeks and hiding any hint that remains of her double chin. She's certainly lost weight but it's a cleverly lit, posed, dressed and angled "after" photo that tricks the brain into thinking she's much slimmer than she actually is. If she were to pose for a photo identical to the first, wearing the same clothing (or as close as possible in her current size) then it would be obvious that although she's smaller she's still by no means a healthy weight. All in all, she's not as fat but she's still fat.