As Scout listens to the testimony of Tom Robinson, Scout reasons that Mayella Ewell "must have been the loneliest person in the world," even more so than Boo Radley. For, when Atticus asks her if she has any friends, Mayella is confused by his question, not knowing what he meant; moreover, she interprets his question as an attempt to ridicule her.
Scout deduces that Mayella is a social pariah; she lives by the garbage dump in squalor and is shunned by white people. And, because she is white, the black residents of Maycomb avoid her. Clearly, Mayella's calling to Tom Robinson indicates her terrible loneliness as she is left by herself most of the day, Scout figures; further,
Tom Robinson was probably the only person who was ever decent to her.
But, when she is in the courtroom before the white people, she says that he has taken advantage of her, and as she steps down from the witness stand, she looks at Tom "as if he were dirt beneath her feet."
Perhaps better than any other courtroom scene, this one demonstrates the skewered values of the Ewells. When she was lonely and craved attention, Tom Robinson was called to and appreciated. But, faced with the jury of twelve white men and threatened by her brutish father, Mayella hypocritically acts as though she is superior to Tom and has not wanted his attention. She cares not for his welfare and is only concerned with how she appears to the jury and those in the courtroom.