Amy Jackson- Orual's Jealousy

The sisters, Psyche and Orual, have an interesting relationship in Till We Have Faces. Psyche is beautiful and Orual is unattractive. Orual has a strong love for her sister. She has a jealous love for her. How is the is the bond between Psyche and Orual stronger than that of friends? Is the sisterly bond stronger because of blood or experience? Orual is jealous when Psyche is "stolen away" from her. She does not think about how Psyche feels about it. Orual has a selfish love for Psyche. Lewis writes in The Four Loves, "Friendship is the least jealous of loves" (61). Is that only true if one has no other friends or a lover? If a friendship is the only love that someone has, then their friend will inevitably disappoint them. They will love someone greater, with an Eros love. Is it dangerous to put all one's love in a friendship?