In To Kill A Mockingbird, Mayella Ewell is the girl who looks to Tom Robinson for sympathy and who, on discovery by her alcoholic father that she tried to kiss a black man would rather lie to save herself than admit that she has falsely accused an innocent man who now stands trial for her rape and assault. In Maycomb County, it would be unacceptable for a white girl, regardless of being "white trash" to do such a socially unacceptable thing and the town's folk therefore will have no hesitation in finding Tom guilty as it is inconceivable to even consider that a white person might do such a thing.
The reader is aware of the type of family that the Ewells represent. Even Atticus who judges no one and who feels sorry for Mayella is aware that "the Ewells had been the disgrace of Maycomb for three generations" (ch 3) and that they live "like animals." Mayella's father does not care for his children and the task falls to Mayella. Mayella's brother Burris is in Scout's class at school and causes consternation when he is taken to task for the lice in his hair. His unsuspecting teacher does not realize that the town makes concessions for the Ewell family. In chapter 3, the reader knows that "the whole school's full of 'em. They come first day every year and then leave." It is pointed out that there are "numerous offspring."
It will only become apparent later just how many there are; during Tom's trial when Mayella gives her testimony and which number Tom confirms during his. Mayella has seven siblings.
According to Scout's school gossip (in Chapter 17), "nobody was quite sure how many children were on the (Ewell) property." Some thought there were six, and others said nine. Scout only knew that there were dirty Ewell faces pressed against the windows of the house when people passed by. However, Mayella Ewell knew how many brothers and sisters she had, and she revealed the answer while she was on the witness stand (in Chapter 18). When Atticus asked Mayella how many brothers and sisters she had, Mayella answered,
Assuming that Mayella meant "seven," that would total eight Ewell children, counting Mayella. (Mayella, 19, was the oldest, and the only other child mentioned was Burris, Scout's lice-ridden classmate.) Tom Robinson confirmed this number when he took the stand (in Chapter 19). He claimed that Mayella told him that it
" 'took me a slap year to save me seb'm nickels, but I done it.' "