Who is Annie Robicheaux, nee Ballard from Heaven's Prisoners and what is their importance?

Annie Robicheaux, nee Ballard, is a thirty-something white woman from Kansas. Nominally raised a Mennonite, Annie does not fit in with the dominant social milieu of New Iberia but is nevertheless widely accepted because of her graciousness, intelligence, and kind heart. She is described as physically attractive, with golden hair, white skin and large breasts. She has a well-developed sex drive and likes having sex in the open and is generally unconcerned about being seen having sex. She and Dave have been married only a few years when the novel opens, but Annie is fully accustomed to her new life and moves with ease around the house and area. She is particularly beloved by Batist and his family and has managed to settle down Dave's wilder streak.