The primary difference between Dee's attitude and her mother and sister's attitudes can be summed up in Mama's simple statement that "Dee wanted nice things."
Mama describes Dee as someone with a strong, sometimes antagonistic personality who seems to have forged her sense of identity in opposition to her mother....
What Mama values, Dee rejects. What Dee embraces, Mama either does not understand or—more tellingly—Dee does not permit her to understand. This is illustrated by the way Dee insists on reading aloud to Mama and Maggie "without pity," as Mama says. Dee wants to display her education but at the same time to exclude her family from it. Mama says of Dee, "[she] pressed us to her with the serious way she read, to shove us away, like dimwits, at just the moment we seemed about to understand."
Dee wants nice things, and she wants those things for herself.
This has been her approach to the world her whole life, so it is not surprising to Mama that Dee applies that same approach to her heritage as a Black woman from the American South. Dee doesn't want the rough-and-ready truth of her upbringing, with Mama's large, work-calloused hands, her slow-witted sister, Maggie, or the tumbledown house she grew up in. Dee wants to transform her heritage into something beautiful with inherent meaning that outsiders will instinctively appreciate.
She comes to Mama to pick and choose those parts of her heritage that best serve her purpose. Just as she did with her education, Dee seems to flaunt her "superior understanding" of her family's heritage while at the same time trying to cut her mother off from it. Dee doesn't want a quilt because it is a quilt; she wants a quilt to hang up as an artwork. She wants to transform Mama and Maggie's life into a quaint cultural tableau which she can show off to others with pride—and to deny her mother and her sister the opportunity to actually live their experience.