Who is Miss Mackenzie from Somewhere in the Darkness and what is their importance?

Miss Mackenzie is an elderly woman in Arkansas who takes Crab and Jimmy in as soon as they arrive. Miss Mackenzie does not appear to be related to the Littles, but is a close friend to the family, something like Mama Jean. In the end Miss Mackenzie delays the inevitable by warning Crab that Rydell has returned to the house with the police.