Joan Gillespie, who spent 16 years as director of development of the Stone Ridge School of the Sacred Heart, a Catholic girls school in Bethesda, died June 5 at her home in Chevy Chase. She was 78.

  The cause was supranuclear palsy, a progressive neurological disorder, said her daughter Joan Swift.

In 1991, Mrs. Gillespie left Stone Ridge School and worked until 2010 as a residential real estate sales agent with Cathie Gill Inc., a Washington real estate firm.

Joan Gisella O’Neill was born in St. Louis and moved to the Washington area in 1945. She was a 1952 graduate of Georgetown Visitation Preparatory School and graduated in 1956 from what is now Trinity Washington University.

Earlier in her career, Mrs. Gillespie was a model and buyer at Garfinckel’s department store in Washington.

She was a member of the Catholic Shrine of the Most Blessed Sacrament in Northwest Washington, the Chevy Chase Club and the Sulgrave Club.

Her husband of 23 years, Julian E. Gillespie Jr., died in 1982.

Survivors include five children, Joan Swift of Sun Valley, Idaho, Ellen Clare Dreyer and Elizabeth Billings, both of Washington, Julia Sanders of Kensington and Julian Gillespie of Stonington, Conn.; four brothers, John O’Neill of Bethesda, Brendan O’Neill of Chevy Chase, Justin O’Neill of Guilford, Conn., and James O’Neill of Kensington; a sister, Christine Gremp of Riverside, Conn.; and 14 grandchildren.

— Bart Barnes