"@dwinblood she shouldn't be angry."
In the hypothetical scenario described, angry is completely understandable and should be expected. Nepotism masquerading as a meritocracy will naturally cause envy and anger.
Your parent analogy doesn't work. You don't seem to be taking into account that other peoples payouts are diminished by these actions.
If you want to use a parent analogy it would have to be along the lines of a team coach that always gives their child far more time on the field than the other child. If your kid wasn't getting any time on the field despite being an amazing player because the coach keeps putting their less than stellar child in you are going to be mad.
I don't think telling people that their very natural emotions are invalid is the right way to approach this problem.