It seems as though Walker does not want us to agree with Dee or Dee's ideas about heritage because she presents Dee as a relatively unsympathetic character. She's described in ways that make her presence seem painful or damaging to her family: she "burned [them] with knowledge" when she was young, and she insisted that she would come to visit her mother and sister -- though she would never bring her friends -- because she seemed to be embarrassed about where and how they lived. When she returns home, she is unkind and selfish, insisting that she be allowed to take items from her mother's house that her mother and sister still use.
Mama and Maggie, on the other hand, are very sympathetic. Mama longs to have a good relationship with Dee, and she feels the sting of their alienation from one another. Maggie is quiet and reserved but ultimately generous and kind. They prize their heritage by keeping family stories alive, by knowing family history, and by using -- everyday -- the items hand-made by family members; this way of viewing heritage seems to keep it alive, in the present and not stuck in the past. Dee, however, sees heritage as something to preserve and hang on the wall, something to show off but not to use, and certainly not to put to "everyday use." In fact, she criticizes Maggie because she believes that Maggie would destroy their heritage by using these items each day. Because of the way Walker presents these three characters, it seems as though she wants us to agree with Mama and Maggie's view of heritage: it is best kept and appreciated through frequent use and remembering, not by hanging it on the wall. Heritage is in the stories that Dee doesn't know, not the quilts that she so desperately wants.