What is the main conflict in Till We Have Faces by C. S. Lewis?

Till We Have Faces explores Queen Orual's lifelong battle to reconcile her religious heritage with her Greek tutor's agnosticism, brought into conflict when her beautiful sister, Psyche, believes she has become the sacrificial bride of the Wind-Spirit and loses him, when Orual demands proof. In old age, Orual writes and then appends corrections to her telling of the story, sure some day that wise Greek readers will judge between her and the gods.