What causes tension between dee and mama

I think Mama finally gets fed up enough to let Dee go. Dee has used both Mama and Maggie as a sort of cultural side-show. Dee is condescending towards her own family. Maggie hides in the shadows while Mama tries to appease Dee's demands. Finally Mama tells Dee what she can take and what she can't and then sends her away There is the understanding that Maggie, with all her imperfections, is her only daughter now.