Dee (Wangero) is the character who most fits the notion of the antagonist. Dee doesn't hate her mother and Maggie. On the contrary, she has some good intentions. She wants them to have better lives. The problem is that, for Dee, that means a more modern life. Mrs. Johnson and Maggie are comfortable with the way that they live, so they are resistant to Dee's suggestions. Dee is condescending towards them.
The argument over the quilts really exposes the differences between Dee and Maggie. Dee has always been interested in fashion and style. While there is nothing wrong with that in general, we do see that Dee's obsession with style is largely superficial. Her new interest in African culture is also largely superficial. That's why it is hard to suggest that she is simply another protagonist who's chosen a different worldview. Dee's worldview, via this newly claimed African heritage, is still superficial. When she wants to take the quilts, she wants to display them. Maggie, on the other hand, would use them as they were intended.
Connecting with her African heritage is admirable, but not if its purpose is a superficial display. When Dee abandons her American familial heritage, this is a symbolic break. Walker uses the metaphor of the quilts to show how families are connected. Quilts might be made from various scraps of clothing, including ancestors' clothing. These scraps are then connected, and this symbolizes the connection of current family with previous generations. Dee doesn't appreciate her family history and this is shown through how she views the quilts. She wants to display them. She doesn't want to use them as blankets, and thus avoids practically and intimately connecting with her family and ancestors.