In 2008, Union appeared on "Ugly Betty" for three episodes as Renee, Wilhelmina Slater's sister and Daniel Meade's love interest. She also made a cameo appearance in the music video for Ne-Yo's "Miss Independent". Union appeared in the 2008 film "Cadillac Records". She was reported to have signed to the film in March 2008. She portrayed Geneva Wade, who later married Muddy Waters. Union was seen as a "pleasant surprise" in the film, and her performance was said to have shown she had larger acting range than her previous roles. Union later called taking the role of Geneva Wade in the film the best business decision she had ever made. Union appeared in the 2008 film "Meet Dave", playing the love interest of the title character. Union said the film was a gift. That same year, she wrote the foreword for Hill Harper's "Letters to a Young Sister: DeFINE your Destiny". Union joined the cast of the U.S. television series "Life" on NBC and appeared in four episodes prior to its cancellation in May 2009. She appeared in the ABC series "FlashForward", a role for which she was nominated for an NAACP Image Award for Outstanding Supporting Actress in a Drama Series in 2010.