Who is Aunt Mae Gebler from The Neon Bible and what is their importance?

Aunt Mae is David's aunt, who comes to live with the family after many years as a struggling singer. She is a heavy set woman, around sixty years of age, who dresses in bright colors and big hats. Her stage name was Mae Morgan and she has trouble adjusting the likes of a small town after having big dreams in the music industry. She is the sole confidant and best friend to David.