Both the historical and philosophical context of "The Edible Woman" denote the struggle for self-acceptance and the eternal quest for who you really are.
Marian's role as a woman has been delineated from the beginning: By family, society, her fiance, and her own self. She has been basically told what she, as a woman, is supposed to be. The test of actually baking a cake in the shape of a woman is a symbol of the secondary status that she felt she was expected to fulfill. Taking a bite out of her woman-shaped cake was a metaphor of taking a chunk off her personal conventions about what womanhood is, and also is an impasse when she finally makes peace with herself and asserts her own ideals.