As a former anorexic and bulimic, I don't get any disordered eating vibes from Grace (and I was hospitalised for years due to my EDs)
I know a girl JUST like Grace - looked like her, acted like her and from a super Christian family. Grace really reminds me of her, and what's more, this girl was super skinny, just like Grace is.
There are people out there who are naturally incredibly thin and have absolutely no issues with eating or food. Zoella is an example of someone with this similar structure, and I know two girls in real life who have that physique too. No eating disorders at all - eat lots of food and gain no weight.
They're like the rare unicorns (they have male metabolisms from what I can see haha, but their's don't age like boys' do!)