Aunt Alexandra went to stay with Atticus in order to help around the house during Tom Robinson's trial and to teach Scout how to be a proper and strong lady, just like her.
Because she decided that it would be good for Scout to have some feminine influence. Aunt Alexandra told Atticus that Scout has to try to behave like the young lady that she is. She does not think that Jem and Scout are being raised properly Alexandrea has her own ideas and strengths. Because of this she has a strong feminine role in the community and fits well within Maycomb.
They certainly welcomed her and even said it is "as if she had always lived with us..." She gave many nice and long visits to the members of the town. She got very involved within the town and joined the Missionary Circle of the Maycomb Alabama Methodist Episcopal Church South and becomes the secretary of the Maycomb Amanuoensis Club. In the end of the book, and at the end of the trial, she ends up staying in Maycomb as well!