Meh. I teach high school and there is a lot of variation in when kids start to look more adult like. She passes as a 16 year old. Also, it is pretty normal for Swedes to have weird accents when they speak English. They are not taught the differences between American accents and British accents.

I still agree that her fame is totally manufactured. Her parents ought to be in prison.

It is not an English accent - source: me, in England for a long time. Nobody sounds much like that.

She did have a period of not eating, or limited eating, so was likely undernourished. I don't think it was long enough to make her this way. Maybe she's just small.

She's got a sister, two years younger. Compare their faces here:

https://heavy.com/news/2019/09/beata-ernman-thunberg/

The sister looks the same height and has a normal face. It emphasises that there is something wrong with Greta. If anything, it makes her look about 2 years older than Greta. Greta has a rounder face, squinty eyes, thin lips, no chin. There have been a lot of speculations about the cause of Greta's looks, but it is especially enlightening when we compare her to someone with 1/2 the same genes that we can see what she should have looked like.

I've encountered dozens of young swedes whose english abilities are so advanced that they make me think they are from UK or USA. Nothing strange about that, in my opinion.

I dunno what greta sounds like, never bothered to hear her speak... but a lot of nords can absolutely pass for native speakers.