Ady was born in
Edgcote in Northamptonshire in 1881, the only child of Rev. William Henry Ady, a clergyman, and his wife,
Julia Cartwright Ady, a biographer and an amateur expert on the
Italian Renaissance. She was the great-granddaughter of
Thomas Fremantle, 1st Baron Cottesloe. Her mother's interest in Italy had been fired by her cousin,
William Cornwallis Cartwright. Her mother took responsibility for Cecilia's education, and Cecilia obtained a place at
Oxford, where she studied at
St Hugh's Hall, and obtained a
first in the honours school of modern history in 1903 (although women were not at that date entitled to be awarded degrees). She became a protégée of the historian
Edward Armstrong. In 1909 she joined St Hugh's as a tutor, where she developed a close relationship with the college's principal,
Eleanor Jourdain. Jourdain eventually turned against Ady, allegedly jealous of her popularity. Ady protested, and a mass resignation followed, which included six of the college's council. The matter became of wider public interest, and
Lord Curzon (the
chancellor of the university) was asked to investigate. Ady's name was eventually cleared, and Jourdain died just before she was to be asked to resign. The inquiry resulted in improvements to the employment conditions of female tutors. Ady then became a tutor with the
Society of Oxford Home-Students. In 1929 her old college re-employed her as a research fellow. In 1938 she was awarded the degree of
Doctor of Letters (DLitt), after she published a monograph titled
The Bentivoglio of Bologna: a Study in Despotism (1937). Ady died in Oxford in 1958. Following her death, her colleagues and former research students compiled a
memorial volume of donated essays, titled
Italian Renaissance Studies (1960). ==Works include==