In To Kill A Mockingbird, why is Mayella Ewell considered lonelier than Boo?
Boo has no one. Mayella has her siblings. Yet, why does Scout think that she's the loneliest?
'Mayella Ewell must have been the loneliest person in the world.'
All of the aspects of Mayella's life as presented above contribute to her loneliness, but I think the full answer goes deeper than those issues. The other Ewell children live in the same environment but are not presented to be as lonely as Mayella. The difference is that Mayella loves beauty. She yearns for beauty so much that she plants geraniums in slop jars, and the beauty of the flowers contrasted with the dirtiness of the rest of the property "bewildered Maycomb." In a similar manner she yearned for love so much that she dared to break one of the strongest taboos in her society to try to satisfy her desire. So Mayella was separated from her family by a nature that yearned for beauty and love, foreign to the Ewells; as well as being separated from the rest of the town by the slovenliness, laziness, and generally poor reputation of her family. Finally, the incident, trial, and death of Tom Robinson made her further ostracized by the town and even more at the mercy of her abusive father.
Mayella has siblings, but they are anything but a close family. She must keep the house for all of them, including her father. Her father is a mean, horrible man who abuses her. The book never says whether Bob Ewell, her father, sexually abuses her, but it is possible. Mayella lives in the depths of poverty from which there is no escape. She has no one her age to talk to or to care about her. Her future doesn't look bright either, being the poor white trash of Maycomb.
Even though Boo has been in seclusion, he is a kind, gentle man who hasn't let his isolation make him bitter. He lives in a nice house and seems to have made his life bearable by watching life out of his window. He shows his kindness when he puts a blanket over Scout the night of the fire. His rescue of Scout and Jem from Bob Ewell in the end further demonstrates what a gentle soul Bob is.