Spencer-Churchill served as a maid of honour to Queen Elizabeth II at her coronation in Westminster Abbey on 2 June 1953. She was the eldest and highest ranking maid of honour at Elizabeth II's coronation, as the only daughter of a duke. Lady Rosemary, along with Lady Jane Vane-Tempest-Stewart, rode in a carriage with Charles Tryon, 2nd Baron Tryon, the Keeper of the Privy Purse, during the procession while the other maids of honour waited at the abbey. After the coronation, Spencer-Churchill returned to Blenheim to attend an outdoor party hosted by her mother, the Duchess of Marlborough, where they roasted an ox for villagers from Woodstock.