Who is Auntie Braxton from Jacob Have I Loved and what is their importance?

Auntie Braxton is described as a old "cat woman", who lives alone and prefers the life of a hermit over socializing with her neighbors. She marries the Captain after suffering a stroke, and although their marriage begins as a marriage of convenience, he comes to love her very much. Auntie Braxton dies after suffering a second stroke. For Louise, she becomes a symbol of what she might become if she stays on the island..... and is one of the reasons for her leaving.