Who is Heidi Milligan from Night Probe! and what is their importance?

Heidi Milligan is a commander in the navy and a student at Princeton. She graduated from Annapolis, is currently divorced, and is focused on her career. Heidi's research uncovers a letter that refers to a treaty that was put aside and negated by William Jennings Bryant and Herbert Henry Asquith. Curious, she begins to follow the trail of clues about the treaty. When she leaves for her navy assignment on the West Coast, Heidi meets Brian Shaw at a party. She leaves with him for a night in Santa Barbara, and then she tells him that Dirk Pitt has her notes on the North American Treaty. She gives him Pitt's address and other information that helps him in his search.