Why do people keep doing the same thing they are not good at?

I have this coworker I tried to assist on how to make jewelry for over a year now. Shes the one who asks questions but then never takes my advice. She gets rude anymore. There is no right or wrong way but there are guidelines to follow. She even insisted that a company made a bead wrong even after I explained that it wasn't made to be a focal piece the way she was trying to use it. Her designs lack what they need to be complete although her choice of beads are nice and eye catching. There is always something missing. Her loops are uneven making the earrings dangle uneavenly. Her stranded necklaces have huge gaps between the last bead and crimp bead as if she isn't even attempting to make it properly. This one elderly woman who never speaks negative words, everything is beautiful and wonderful has my coworker big headed. So much that she now flaunts her work. She handed out earrings to all the ladys that I would be embarrassed to give. She gave me a pair. My cousin seen them and after I remade them. He said that they looked a hell of alot better. Why do people think they're doing well when they're not? Why are these people so nieve to false complements? I mean like if you're not good at sports, then don't play. If you can't swim, don't get in the water. And if you can't make jewelry, then please don't. As m I right or wrong here?

Well, I think you should let them try. She keeps trying. Let her try. She'll eventually learn from her mistakes...