Cheryl Farley was a young woman who believed in astrology and was paying Martin Trueman to make predictions for her. Her husband Stuart thought that she was wasting their money.
When Trueman was taken by the Ancient Lights, he used their power to take control of Cheryl's mind, making her his servant. He made her give him all her money, leave her husband and become his assistant on his shows.
When Luke Smith stopped the Ancient Lights, Cheryl was freed from Truman's control and returned to Stuart. (TV: Secrets of the Stars)