Well people from other countries were always mixing together, what if she has a non-Korean/non-Asian in her family tree and she does not know about that? Or she has an anomaly in her genes, that happens too. I know there will be always big suspicions about plastic surgery, but only she knows if she did it or not.
The Golden ration is bullshit, since it is all about one number and face symmetry. And those people who have it looks just normal. Face features trends change a lot after short periods of time. (for example, oval, heart face shapes, big eyes, sexy mysterious eyes, small round nose, sharp nose, small doll lips, big plump lips, etc) Cleopatra was Caucasian since she was Greek. Tall nose bridges are a predominately Caucasian trait, because anatomy. That is one of two (the second are the eye sockets) main differences between Asian and Caucasian.
She could have reflux, or inflammation of the esophagus, stomach or other organ. And yes stress and wrong diet (for example ED) can be the cause. Hope they will find where is the problem and she get's better soon.
Yes, I am pretty much sure that "Dumi" is just her youtube persona. like that saying says "She kills two birds with one stone." Not only she has the attention from her Naive fans, but in same time produces people who dislike her. On youtube it does not matter, if its a like or dislike, a positive or negative comment, also every view count. But sure to take everything and play this theater the whole time is a very special personality needed. (For example her English, she reads PULL and makes it sounds on purpose even worse.)