​From Wikipedia, the free encyclopedia. Deborah Rennard (born November 4, 1959) is an American actress. She remains best known for her recurring role in Dallas as J.R. Ewing's secretary Sylvia "Sly" Lovegren. She appeared in the series from 1981 to 1991 and also in the film J.R. Returns. She also appeared as Harmony in the movie Land of Doom (1986 film) and as Cynthia alongside Jean-Claude Van Damme in the... see more