Well, in my opinion, his face on fan art is very far from the original one, both in color and in features.
I doubt that Kora's features and skin color can be considered as "ugly". I would suppose, that:
1). Probably, the most of people around the author of fan-art are light-skinned, so (s)he just get accustomed to imagine ight-skinned people, and their drawings have corresponding bias. I suppose so, because I've noticed such a bias in myself some time ago.
Btw, I've started to notice the existence of this bias in my own mind, only after I spent several months at this forum. There are many artists from different countries here, who draw people with different skin colors and facial features. Only when I've got accustomed to this diversity, I've realised that I had a bias to make everyone "whiter", because previously my brain got accustomed to see almost only ppl with more-or-less lighy shades of skin around (in Moscow you rarely can meet a person with a significantly dark skin).
It's not cool, and now I'm trying to get rid of this bias. Seeing people of different skin colors in London now also helps me a lot to get more accustomed that people can have all shades of colour, not only light shades, and remember this. But maybe that artist just haven't think about all of it yet. As I said, it's hard to notice from inside.
2). The style of drawing of this artist itself looks veeeery far away from your own. This also maybe a reason why it's so hard for them to draw your character's face close to the original. Again, this is probably too far away from what they used to draw.