I think she may naturally be a thin person, but it looks like she has lost weight since her videos in 2013. I found it interesting that while she was talking about her weight in a video, she mentioned her doctor "thinks everything is fine," and was subconsciously shaking her head "no" while making the statement. That is sometimes an indication that a person is telling a lie, although not always. Her channel looks like it is focused around makeup, fashion, and likewise her body image, so her success is also somewhat tied to her weight. Changing her weight at this stage probably seems scary to her as it may change her success (in a possibly a good way, or possibly a bad way). To be honest, her weight, and why she is at her current weight, is really none of our business...
Losing weight could happen from a variety of things, not just anorexia. I dropped an awful lot of weight (somewhere between 35 - 45 lbs or so.. I'm not really sure how much I lost tbh, but I definitely became very underweight) before I figured out it was Celiac Disease. x_x It could be type-1 diabetes, some medication that she needs to take...It could be a lot of different things. It's not fun to be called an "anorexic bony twig," so I hope people stop commenting on her weight. It's not right to skinny-shame people, just like it's not right to fat-shame people.
She shouldn't be banned from YouTube because of her looks. YouTube wouldn't ban an overweight person for making fashion videos (actually...a lot of Americans would probably praise a channel for making overweight fashion videos...), so why should they ban an underweight person for making fashion videos?
She somewhat reminds me of Lizzie Velasquez -- a young woman who has a rare condition that prevents her from accumulating body fat. Some people are really slim and cannot help their appearance. Whatever the situation, her family and close friends would know more about whether or not her weight has drastically changed. I cannot decide from only looking at pictures that always show her as a very thin person. I would imagine that her family is aware of any issues that may be present, and that they are doing what they can to help and support her.