Who is Ms. Dietrich from Legends of the Fall and what is their importance?

Ms. Dietrich is Nordstrom's secretary. She is married, in her thirties, and works hard enough to run the whole company. Unsatisfied with her sex life, Ms. Dietrich makes a move on Nordstrom one night. At Nordstrom's farewell dinner, she plans to bed him again, but she ends up drinking too much and has to go home.