Based on Mayella's testimony, how is it flawed when compared to her father's testimony

Atticus asks if Mr. Ewell is a loving father, and with hesitation, Mayella says that he is "tolerable" except when he has been drinking. However, she insists that he never lays a hand on her or beats her. Atticus asks for more details about the struggle, then he asks many questions which Mayella doesn't answer: Why didn't the other children hear her screaming? Where were they? Why didn't they come running? Did she start screaming when she saw her father in the window? Did she get beaten up by her father, not Tom Robinson? Mayella just says that she was taken advantage of, and if the upper class gentlemen won't prosecute Mayella can't answer any of Atticus's simple questions while her father made up lies.