Not gonna quote the multiple replies already that had similar sentiments, but...
A 15 BMI would be moderate bordering on extreme anorexia, clinically speaking, which carries a high risk of death, and permanent organ damage. Let's not get confused on this thread - I know nothing about this person's actual BMI because by now we should all know you can never guess a person's weight by looking at them (UM - DUH that has nothing to do with how science works), but anyone who has a BMI like that is not "normal healthy," "fit," or "not that skinny."
We need to check the insane lies we tell ourselves and others on this forum every day.
Someone who has a smaller BMI than 99.9% of the global population, is NOT normal, and is not likely healthy. Also, we are all well aware that both the fashion/modeling industries, and East Asian culture, prize thinness and encourage extreme behaviors and eating disorders, so someone who is considered thin and "attractive" in an East Asian modeling world, is likely doing an awful lot of harmful shit to themselves to keep their career. Which is exactly why we now know of a number of deaths, confirmed eating disorders, drug addictions, and suicides in the East Asian entertainment and modeling worlds.
I wish her happiness, balance in her life, and health. But also, very few people on Earth will ever be able to look like her, no matter how much starving they try to do or surgery they pay for.
I'm glad that the pics included above at least don't look terrifying. But perhaps they're just the angles and clothes, and other photos would be much worse.
If stats mentioned online are to be believed, whether or not she has an underweight or borderline underweight BMI, she does have extremely abnormal body proportions. Being 5'10" and a South Korean female is unusual already - the average age for South Korean women is currently about 5'4". And if so, her measurements are bizarre and seem like they would not hold up her tall body well, and might cause medical problems. That could be totally natural, and something she was just born with. But... a lot of times very unusual proportions in models/actors, is not natural at all, and indicates surgery and disorders.
Thank you so much for being the voice of reason here.
Your presence is appreciated. <3