Who is Bronwyn 'Stormy' Llewellyn from Odd Thomas and what is their importance?

Bronwyn Stormy Llewellyn was orphaned as a young child. Shortly after their deaths, she was adopted by a man who sexually abused her. Stormy told a social worker, and she was then allowed to live with her uncle, who was a Catholic priest. Stormy met Odd Thomas in high school, and the two have been dating ever since. Despite believing that they're meant to be together forever, Stormy refuses to marry him or to share the intimacy of sex.