Who is Lady Jessica Atreides from Dune and what is their importance?

Lady Jessica Atreides is Paul Atreides' mother. She is a trained Bene Gesserit sister, who left the order sixteen years earlier as the concubine of Duke Leto Atreides, the ruler of Caladan. Jessica is described as tall and thin with an oval face, hair the color of polished bronze, and wide-spaced and green eyes. The Mentat Thufir Hawat, in charge of security in the new home, finds a partial note that suggests Jessica is a traitor, but Leto refuses to believe it. He does, however, allow her to be put under constant surveillance by Duncan Idaho. When Jessica learns she is being watched, she confronts the Mentat Thufir Hawat, whom she suspects of being the traitor. It is, in fact Dr. Yueh, who drugs her and Paul to be bound and sacrificed in the desert, but also plots their deliverance.