Adeline Louisa Maria de Horsey was born in London to an aristocratic family, a daughter of Admiral Spencer Horsey Kilderbee and his wife, Lady Louisa Maria Judith Rous. When she was a small child, her father adopted the surname "de Horsey," his mother's maiden name. She was educated by French governesses, and was an accomplished musician and horsewoman. In 1848, she became engaged to Infante Carlos Luis Fernando de Borbon, conde de Montemolín, a claimant to the Spanish throne; but she broke off the engagement in 1849. In 1857, she began keeping company with James Thomas Brudenell, 7th Earl of Cardigan, who had become famous for leading the Charge of the Light Brigade in the Crimean War, and was a friend of her father. He was married at the time but separated from his wife. Adeline took a furnished house in Park Lane, and became the Earl's mistress until they were able to marry in 1858. This state of affairs caused a great scandal in society and Adeline was shunned by most people of her class. Queen Victoria refused to receive her at Court, and she was barred from fashionable entertainments. The Earl died in 1868, and Adeline remarried in 1873 to Don Antonio Manuel de Saldanha e Lancastre, conde de Lancastre, a Portugese nobleman. Against the usual protocol, she merged her former title with her new one and styled herself Countess of Cardigan and Lancastre. The couple lived in Paris before the Countess returned to England in 1879, although she regularly continued to visit her husband. She wrote a volume of scandalous memoirs entitled My Recollections (1909).