what from mayella's testimony would leave one to believe she is lying

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 if this was the first time Tom Robinson has been invited into her house, and she jumps a little before she says that it was the first time. He asks Mayella if she remembers being beaten in the face, and Mayella first says no, but then yes.