How has Dee forgotten her heritage in "Everyday Use"?
Dee has forgotten her heritage because she has embraced some of the philosophy of the Black Power Movement, a movement which wished to establish an identity for African-Americans completely apart from white history.
Although Dee, now having taken the African name Wangero, declares that she is reclaiming her heritage by taking old items from the family, she has actually rejected her family history by wishing to merely put the family items on display. In her actions and remarks to her mother, she demonstrates a belief in what Malcolm X's brother Reginald told him, "The black man is the brainwashed." For, she is now convinced that she should reject anything connected to white society such as certain names, historical events, and customs--all part of the "brainwashing" by whites of African-Americans. Now, she tells her mother that can no longer bear having a name from people who have oppressed her. Furthermore, when she first arrives, Dee/Wangero snaps pictures of the house and dirt yard as though she is composing a documentary for the government on how the underprivileged live.
Because of her behavior, Mama refuses to give Dee the quilts after Dee asks for them; instead, she hands them to Maggie, who appreciates the collection of pieces of Grandpa Jarrell's Paisley shirts, Grandma Dee's dresses worn fifty years ago, and other memorable items such as a small piece of faded blue that is Great Grandpa Ezra's Civil War uniform. Indeed, it is Maggie who understands that the act of quilting by the female members of her family has been an act of connecting the family's roots and past events together in memory. The quilts symbolize the heritage that Dee has forgotten. And, for this reason, Mama refuses to give Dee the quilts.
As Dee departs wearing her over-sized sunglasses, Maggie smiles a "real smile, not scared" anymore; and, long after Dee's car is gone, Mama and Maggie just sit outside, "enjoying until it was time to go in the house and go to bed."