Scout and Miss Maudie had a special relationship. Miss Maudie was the only adult that the children responded to without a hint of reservation. She was able to act as a bridge between two worlds - the adult world and the world of children. So, when the children did not understand something, Miss Maudie was always a voice of reason and a guide. She also spent a lot of time with the children. Here is as quote to support this point:
In summertime, twilights are long and peaceful. Often as not, Miss Maudie and I would sit silently on her porch, watching the sky go from yellow to pink as the sun went down, watching flights of martins sweep low over the neighborhood and disappear behind the schoolhouse rooftops.
For this reason, Scout grew close to Miss Maudie. In fact, one of the most important lessons that Atticus tried to teach his children was never to shoot a mockingbird. Being children, Jem and Scout did not understand, so they asked Miss Maudie. She explained Atticus' reasoning. Here is the quote:
“Your father’s right,” she said. “Mockingbirds don’t do one thing but make music for us to enjoy. They don’t eat up people’s gardens, don’t nest in corncribs, they don’t do one thing but sing their hearts out for us. That’s why it’s a sin to kill a mockingbird.”