Superficial knowledge is irrelevant to wisdom of knowing the human heart. It also has to do Rosamund's looking below the surface. It has to do with her delivery. If she had shared this information stridently and loudly, holding the ruthless prince up for public ridicule, she would never have shifted his reality. Her compassion allows Raphael fall hopelessly and eternally in love, see a way of life he'd never imagined and shift forever his values.
Feminism seems to grow in complexity.
We need characters like Rosamund to enter fairy tales and show our children, male and female, models of humanity.