Who is Sara Rosen from Jack and Jill and what is their importance?

Sara Rosen, a former White House employee, is decribed as a sad, lonely woman. Sara has never been married, and she is affectionately known by those who know her as the sexy spinster. As a result, when Brett Sterling begins to lavish attention on her, she immediately falls in love. Sara is unaware of Brett's true identity and will do anything for him..... including murder. .