Yep….certainly is. It’s Nintendo’s intellectual property….even ‘fan art’. I struggled to not comment when I saw her pictures
There are many small businesses that do it and Etsy is awash with Disney and Animal Crossing but they get shut down eventually. Disney and Nintendo are renowned for being very vigilant. I’ve got a small business myself and also have a creative element to it - I wouldn’t touch copyrighted ideas with a barge pole - because my business is worth to much to me, but also from a moral point of view.