Why is Aunt Alexandra at Scout and Jem's house? How does she fit in to the community?

Aunt Alexandra has decided (and convinced Atticus) it would be best for the family if she stays with them for "a while," which worries Scout even though she knows there's nothing to be done. Aunt Alexandra establishes herself in the neighborhood and continues to pester the children about what they should and should not do. She is old-fashioned and proper, and often refers to the people of Maycomb in light of their family history.