Your question touches upon a very interesting question to do with point of view in the story. The narrator, though, is Mama - the mother of two daughters, Dee and Maggie. The mode of narration is first person, and because of this we must be aware that we might not be receiving an entirely reliable narrative - the "unreliable narrator" is a key aspect of first person narration, though perhaps here it is not so unreliable. However it is clear that the speaker is withholding information from both of her daughters. When Maggie asks her, "How do I look, Mama?", her mother dodges the question, and then goes on to tell us the readers how Maggie really looks. We are also left to infer how the speaker feels about her second daughter, the renamed Miss Wangero. However, it is clear from what she says and does that she disapproves of her and her actions.
What is interesting is that by choosing first person narration we are shown up close the various conflicts and tensions that exist in this family between a mother and her two daughters, who have each turned out very differently. First person narration makes this conflict more poignant and understandable, as we are presented with the thoughts of Mama as she tries to work out how to respond to both of her daughters who both have their own challenges.
In addition to describing the narrative point of view as first person, the narrator -- Mama -- is also a subjective narrator: the point of view is first person subjective. What this means is that, in addition to being a participant in the story and using first person pronouns (like I or we), Mama is also narrating the story in the present: as it happens, and not after the fact. You can tell because, when she describes the action, she uses verbs that are in the present tense. For example, she says, "'Come out into the yard,' I say," when she describes talking to Maggie before Dee/Wangero arrives.
First person subjective narrators tend to be somewhat less reliable than first person objective narrators (who narrate in the past tense, after all the action has taken place), because they've had no time to reflect on events. We get their immediate, sometimes emotional, often unfiltered, responses. In a sense, we see these narrators' immediate and truthful reactions, but we don't benefit from their lack of time time to synthesize everything that's happened. With Mama, such a point of view seems to make sense, though. She doesn't try to arrive at any conclusions about the interactions she's had: she takes them at face value, reports them, reports her responses to them, and that's the end of it. The audience is left to draw their own conclusions.