Mayella seems to feel the isolation and loneliness of her racist family more than her father or siblings. She also is the only one who seems to care at all about the squalor that they live in.
It is Mayella who reaches out to Tom in desperation for a friend, it is she who gives small gifts. But unfortunately, her upbringing is too insidious for the young girl to overcome. Readers lose most sympathy for her when she blatantly lies on the stand, and lose it completely when her testimony, though proven false, convicts the innocent Tom Robinson.