At seventeen, Helen was engaged to Commander Price Blackwood, youngest of three sons of the 3rd Baron Dufferin and Claneboye, and Mehetabel Temple; owing to the deaths of his brothers he was to be the future Lord Dufferin, although his parents wanted him to marry more advantageously, mainly based on financial grounds. After their London wedding at St. George's, Hanover Square, London, on 4 July 1825, they went to live in Florence due to the opposition of the marriage by the Blackwood family, but returned two years later with their baby son Frederick, who was born on 21 June 1826. Her sisters introduced her to fashionable circles where she mixed with prominent figures of the time, Mary Berry, Samuel Rogers, Henry Taylor, Brougham, Sydney Smith, and Benjamin Disraeli; Disraeli in later life said she had been "his chief admiration". In 1839, she became Lady Dufferin when her husband inherited his title. He died in 1841 of an accidental morphine overdose; Helen continued to spend her summers at his family estate at Clandeboye in Ireland, which now belonged to Frederick.