For future reference, it'd be very beneficial to include a link to this story, or at the very least the name of the story.
However, I'm assuming the story is "Everyday use" - If this is the case
Dee took on the name of "Wangero Leewanika Kemanjo" due to her belief that her original name was formed from oppression, despite Mama's protest. Dee seems to be under the impression that most of her true culture is a lie and was formed due to racism. She seems to have invented her own culture as opposed to her true culture.