During the Motortown Revue in 1966, Terrell embarked on a torrid romance with The Temptations lead singer David Ruffin. That year, Terrell accepted Ruffin's surprise marriage proposal. After Terrell announced their engagement onstage during an appearance together, she discovered that he was already married. Ruffin had a wife, three children, and another girlfriend in Detroit. This revelation and Ruffin's drug addiction led to violent arguments. Terrell told "Ebony" magazine in 1969 that she believed her emotional state during this relationship was a contributing factor to her headaches, which would come after quarrels. In 1967, Terrell ended their relationship after Ruffin hit her in the head with his motorcycle helmet. It was rumored that Ruffin also hit Terrell in the head with a hammer, which further complicated her unknown condition. However, this rumor was dispelled in Terrell's "Unsung" episode.