Harrison, who went by the name Cecilia, was born to an affluent family in Holywood House, in
Holywood, County Down. She was the third child of Letitia (nee Tennent) and landowner Henry Harrison JP (d. 1873). One of her brothers was politician and writer
Henry Harrison, a supporter of
Charles Stewart Parnell. Her maternal grandfather was
Robert James Tennent, a liberal MP for Belfast. At the age of ten her father died and she and her family relocated to London. Harrison studied at
Queen's College, London where she was awarded a silver medal by University College, London, for painting from the antique style. She studied under
Alphonse Legros at the
Slade School of Fine Art from 1878 to 1885 and won the Slade scholarship. She travelled widely on the continent as part of her studies == Career ==