If Sally finds that doing right somehow violates a need she thinks she has, then that is an issue which would have to be addressed, and which one would have to think about and talk about and so on. We don't want children growing up thinking that doing right is unpleasant. Forcing them to do right against their wishes is thus horribly risky, because it might cause them to drop a theory that doing right is a good idea. Perhaps one of the reasons some parents feel reluctant to intervene in these disputes is that having decided to go for zero coercion, they think they are forbidden from making moral judgments and that everything the children do is right by definition. But that is no more likely than that the children would guess the true theory of physics the first time.
Moral ideas are just as subject to conjectures and refutations as ideas about physics.