Wha why did cousin bud want his daughter to stay with mama

Bud and Mama talk about how he loves his wife and he sees her as a person and not as white. Mama has a hard time understanding or agreeing with him. He mentions his daughter, who is light-skinned enough to pass for white and seems to want nothing to do with being colored. He asks Mama if she can come stay here because it would be good for her. Mama agrees and says she will talk to David.