As Scout and Jem sit in the balcony of the courthouse listening to the testimony of Mayella Ewell in Chapter 18 of To Kill a Mockingbird, Scout whispers to her brother, "Has she got good sense?" Then Scoutobserves Mayella give Atticus "a final terrified glance" before continuing her testimony which has flaws in its credibility.
Clearly, Mayella does not have a healthy family life. With her mother's death, the responsibilities of taking care of the family has gone to poor Mayella since her father is a drunkard. In addition, Bob Ewell is also abusive, and possibly even sexually abusive to Mayella. Since she has to remain in this sordid home, Mayella has few opportunities to make friends; besides, she has no nice clothes or money with which to go to town. Added to this situation, Mayella is a social pariah, labelled by the townspeople as "white trash," so few opportunities for meaningful socialization are open to her.