I lost a tit ton of weight on slimming world years ago, and I was proper skinny, but I didn't even have an ass, I was as flat as a pancake with no definition anywhere. The minute I started doing things like circuits and weight training the muscles in my legs became incredibly defined.Her legs too, the pic of her legs with the mousse shows no muscle definition in her quads at all. As thin as she is you should be able to see them without her even flexing. There’s nothing there. She’s not lifting heavy enough, so her ‘workouts’ must basically consist of lots of cardio based work and very light weight work.
With Gem, she's probably doing weights but she's also still doing lots of cardio and also severely underfeeding herself. Her body won't have the calories it needs to build muscle.