Who is Tammy Hemphill from The Firm and what is their importance?

Tammy Hemphill worked as Eddie Lomax's secretary until he died unexpectedly. Eddie had shared with her some of the details about Mitch's case. Tammy correctly assumes that Eddie's death was related to the work he was doing for Mitch. Fearful for her own life, she contacts Mitch. They agree to stay in touch, and over time Mitch confided in her more. Tammy eventually becomes a big part of his undercover operation. She helps him move and photocopy all of the files he later hands over to the FBI. She is also the woman who seduces and drugs Avery on Grand Cayman Island so that his files and keys can be retrieved.