Killen has spent her working life with the partnership. She joined as an A-Level Trainee in 1982 at John Lewis Bristol where, after several retail roles, she became staff manager in 1992.
In 1995 Killen moved to John Lewis High Wycombe as merchandise manager and later that year was appointed general manager Bristol and then general manager Cribbs Cuseway when the Bristol shop relocated there in 1998.
Killen was promoted to managing director, John Lewis Cribbs Causeway in 2000 and became personnel director for John Lewis in July 2002. She took up her appointment as the partnership's director of personnel in April 2007.
Killen is a member of the Roffey Park Board of Trustees.