Born Margaret Elphinstone in Westminster, London, Rhodes was the youngest daughter of the 16th Lord Elphinstone and his wife, Lady Mary Bowes-Lyon, an elder sister of Queen Elizabeth The Queen Mother.

[6][7] On 20 November 1947, she was a bridesmaid to Princess Elizabeth at her wedding to Philip Mountbatten, Duke of Edinburgh.

[4] In the 2000 Birthday Honours Rhodes was appointed Lieutenant of the Royal Victorian Order (LVO).

She lived in the Garden House, a grace and favour residence in Windsor Great Park.

[11] On 31 July 1950, she married the writer Denys Gravenor Rhodes (1919–1981), with Princess Margaret as one of the bridesmaids.