I don't think it's unfair at all. If LW and her husband earn their money doing something egregiously unethical, well. I'm pretty sure I would favor one child over the other too, if one was Martin Shkreli, Lord of the Pharma Bros, and the other was Jane (as described by LW). And I'm pretty sure the favorite would not be martin.

(I say this as someone who oopsed onto an ethically questionable career path myself and am doing the best I can to go about it in an ethical way.)