Mayella Ewell reveals herself to be a poor, friendless, naive and frightened young woman during her stint on the witness stand during the trial of Tom Robinson. Scout even wonders if she is mentally unbalanced.
I whispered to Jem, "Has she got good sense?"
Jem was squinting down at the witness stand. "Can't tell yet... but she might just be--oh, I don't know."
She believes Atticus's sincere politeness to be mockery, and she exudes a sense of bewilderment throughout her testimony. She is fully out of her element, a teenager who rarely leaves the Ewell house or has social interaction with anyone but her family. Her confused testimony, much of which is untruthful, is barely rehearsed: She contradicts herself when Atticus asks if Tom has hit her, and she later admits, by a nod of her head, that her father isn't always "tollable," especially when he has been drinking. She fears Atticus, but her fear of her father is greater, and it is apparent that she has gone along with his story. When the questions become too much for her, she simply refuses to speak any further.
I guess if she hadn't been so poor and ignorant, Judge Taylor would have put her under the jail for the contempt she had shown everyone in the courtroom... I never saw anybody glare at anyone with the hatred Mayella showed when she left the stand and walked by Atticus's table.