Mama has "promised to give them quilts to Maggie, for when she marries John Thomas." Dee is indeed angry in response, and her reaction is what provides the title of Alice Walker's short story:
"Maggie can't appreciate these quilts!" she said. "She'd probably be backward enough to put them to everyday use."
Dee clearly is judgmental here, characterizing a set of actions as "backward." She's certainly not being humble.
At the same time, though, I wish to provide a counterview to the previous post. I believe that the story is written in a way that biases the reader against Dee and her boyfriend. (The narrator, the very person who feeds the reader all of the information, is clearly biased against the couple. Look at how she mocks their names, for example.) As readers, we're encouraged to see Maggie's receipt of the quilts as a sort of victory. As readers, of course, we can identify and attempt to resist the narrator's bias. I try to get my students to think more about the story by exploring the narrator's bias and by asking them what's so wrong with preserving (i.e. not putting to "everyday use") an item of value. Many of my students have items from previous generations -- china, jewelry, etc. -- that they certainly cherish but don't use every day.
Dee, as expected, is angry. Her mom plans to give her sister a quilt which was made with several family heirlooms such as civil war uniforms, clothes belonging to the family, and other left over important pieces of clothing. Dee, on the other hand, wants the quilt to hang it in her place as if it were a conversation piece (which it was), but she took away the value of the quilt as a symbol of family heritage, and gave it the same importance as a museum piece.
Maggie, on the other hand, is humble and does not mind that Dee takes the quilt, however, deep inside she wants it because she does hold esteem for it as a family heirloom, just like her mother thinks it.
In the end, Mama put her foot down and Maggie kept the quilt.