Diener is President and Owner of Densmore Engines in Fresno and Sacramento and is President of Tavie Farms, Incorporated. She is a former California Council on Science and Technology Member, 1995-2001.

Diener was appointed to former Governor Wilson's State Transportation Commission, 1991-1998, and is a board member of the Fresno Business Council. She is a member of the School Board for the Center for Advanced Research and Technology, the Board of the Futures Institute and the Board of the California State University Fresno Foundation. She is also a board member of the Valley Children's Hospital. She has served as Past President of the Fresno Economic Development Corporation and the Fresno Chamber of Commerce.