What is the importance of "mirrors" in the motion picture, All About Eve?

Each time we see a mirror in this film, one of the characters is learning something more about themselves or someone else. A mirror in most films and books symbolizes the reflection of a person's spirit. A person's attitude and motivations are easily recognizable when they are reflected in a mirror.

We notice mirrors throughout the film. When we first meet Margo, she is adoring herself in a mirror and primping for a wonderful evening. After Eve begins to manipulate Margo's life, we again see Margo's face in the mirror, a face worn with care. In the final scene, we watch while Phoebe takes a bow in Eve's mirror while she holds Eve's award and wears Eve's clothes. Margo may be selfish, but both Eve and Phoebe are cruel and manipulative.