Poor Mayella. She is a character deserving of great sympathy, and it is hard not to feel sorry for the pitiful life she lives in the Ewells' rundown shack adjacent to the dump. But Mayella decides to betray the man she attempted to seduce--Tom Robinson--and, instead, accuses him of a capital crime for which he is innocent. In that regard, she is much like her father: A racist liar who blames others for his own mistakes.
While Bob Ewell has virtually no positive characteristics--he neglects his children, drinks up his welfare check, tries to harm others whenever he can, and (apparently) beats his oldest daughter--Mayella at least tries to make life better for the Ewell siblings for which she serves as surrogate mother. Since Bob does not allow his children to go to school (he and Mayella can read and write a bit, so he sees no reason for the others to learn), Mayella stays at home and takes care of them. She has no social life, and she saves up "seb'm" nickels so she can send the other Ewell kids for ice cream just so she can be alone with Tom. She gets no love at home, and the geraniums for which she lovingly cares are the lone items of beauty on the Ewell property.
Mayella has little choice but to go along with Bob's story after he catches her hugging and kissing Tom, and the beating she takes afterward comes from her father, not Tom. But out of fear for her father, Mayella agrees to back Bob's story: that he caught "that black nigger yonder ruttin' on my Mayella," and she never backs down from her often confusing and contradictory testimony. "If she hadn't been so poor and ignorant," Mayella may have recognized that by doing the honest thing--telling the truth about Tom and letting Sheriff Tate know that her father had beaten her--she would have been able to rid herself of her abusive father and, possibly, begin a new life. With Bob in jail, she would have been left alone with the kids, but at least she would have earned the sympathy--and possibly some help--from the town that her family so disgraced.
he is a bumhole, a jerk and a conniving liar.
She is a poorly abused woman, who has unfortunately picked up a few habbits from her father.