One day Sarah searched a small room off the Queen's bedchamber and stole several pieces of jewellery, a small portrait of the Queen and two of the Queen's dresses. Despite the Queen's enormous array of possessions, the theft was quickly noticed and guards soon arrested Sarah when she imprudently returned for a second helping. Although such a crime was punishable by death, Caroline Vernon took pity on the girl who was merely deported to the American colonies where she arrived in Baltimore in 1771.

She was put up for auction and bought by William Deval, a Maryland planter, but Sarah soon packed her belongings, including the items stolen from the Queen, and escaped to Virginia. Here she passed herself off as the Princess Susanna Caroline Matilda, the younger sister of Queen Charlotte. Her story was that she had quarrelled with the royal family and had been banished to the colonies. She could dress the pad and, having carefully observed the members of the court, could speak and behave in a regal manner.

She was an overnight success in the masquerade. Robert Smyth, a wealthy landowner, invited her to stay with his family and she became the centre of attention at parties, entertaining guests with court gossip. She was the houseguest of many of the richest families and often hinted that she still had influence at court. She had no reluctance to accept money and gifts in return for the assistance she promised. If anyone spoke to her in German where she was supposed to have been born, she would scowl and say, "I am an English princess. English is what I speak."

William Deval in Maryland advertised to get her back, distributing handbills about his runaway servant, describing her as having 'a blemish in her right eye, black rolled hair, stoops in her shoulders'. 'She makes a common practice of marking all her clothes with a crown. Whoever secures said servant woman, or takes her home, shall receive five pistols, besides all costs and charges.'

Sarah was tracked down by an employee of Deval and returned at the point of a pistol. For two years she worked at daily chores until in April 1775 Deval joined the Maryland militia to fight for independence. Sarah took flight again. Having no sympathy for the colonists because in her heart she was still a royal princess, she married a young British Lieutenant William Stirling. After the surrender of the British in 1781, she and her husband stayed on in New York City, a return to England being risky if not impossible.

Sarah still had a handsome sum of money from her career as a princess and she started a ship's chandlers business for her husband. In the boom years at the end of the century and into the new one, the Stirlings prospered, becoming one of the city's wealthiest families. They owned a magnificent home in one of the city's most fashionable areas and several servants at Sarah's beck and call. Thus much of what she had sought in her pose as a princess she eventually attained in her own right.