She was the daughter of George Washington Vanderbilt (1862-1914) and Edith Stuyvesant Vanderbilt, née Dresser. They married in Paris in 1898 and Edith, their only child, was born in 1900. She inherited the Biltmore Estate in 1914. She was married first to Hon John Francis Amherst Cecil in 1924 but divorced him in 1934. She had moved to Paris in 1932 and did not return to the USA. She married secondly Vivian Francis Bulkely-Johnson and lastly, William Goodsir. She and Cecil had two sons, George Henry Vanderbilt Cecil (b. 1925) and William Amherst Vanderbilt Cecil.
She was probably the baby in Portrait of a Baby y549.
On 13 January 1902 her father George Washington Vanderbilt wrote to Whistler suggesting that he painted her. The Vanderbilts were in Europe in April 1902 and although there is no record of Whistler having painted her portrait, Cornelia would have been twenty months old in April 1902, which would suit the age of the child in the portrait.
'Cornelia Stuyvesant Vanderbilt', Find a Grave website.