Look, I get that body shaming is wrong, but Skeletor there needs to eat a cheeseburger immediately. That cannot possibly be healthy.
She's hardly Skeletor. Can barely even see her ribs.
There's some slight definition of the ribcage, but it very much depends on the position of the body and whether the person is putting much effort into exhaling/inhaling as to how visible the ribcage might be / ought to be.
When I was seriously underweight (around the time of my Crohns diagnosis, I was classified as underweight according to BMI), the depth of my bellybutton was barely anything at all (ie. maybe I could get half my fingertip/nail in there). Since then I've put on a couple of stone and I'm back to a normal BMI, my bellybutton now looks deeper, however most of the outlines of my ribcage are still visible, they're just not as stark and obvious as they once were. Despite how much my weight dropped though, I didn't ever look like the worst anorexia pics that one can find on the Internet.
I was about to say that she looks "naturally more skinny", but I wonder through my own experiences whether it's more about one's relationship with food than it is about one's body. I've never been particularly enthusiastic about food, and since the diagnosis I had difficulty gaining weight steadily until I found a safe diet to adopt and counted the calories.
Going purely by appearance, she doesn't look like she's unhealthy per se, but appearances can be deceiving. I personally would question the motivations of anyone actively trying to be any thinner than she is though. I can't help but think though that there's a weird optical illusion going on in that video with the shape of the door (overly tall & thin?).
Does anyone else think she looks like John Malkovich?
I suggest you get an immediate eye exam. Or possibly a more basic exam that involves flash cards and basic object identification.