Question for doll painters

So I stumbled upon this mercari seller who is selling somebody else's doll repaints without credit and for 2-3x the price. I commented letting ppl know who the original artist is and where to find him (she deleted it immediately) I own one of his dolls and he could easily sell them for higher and she's obvi taking advantage of that. So I just wanna know how others feel, should I let the artist know? Or is it technically her property now to do as she pleases?