"(The rumor) got started because the movie had a love scene with Denzel, and people took that and translated it to real life," the 34-year-old actress tells the magazine, now on newsstands.
"They said I was pregnant with Denzel's child, and people were calling my mother, saying I'm having his baby. It's frustrating. People are going to talk no matter what."
Washington, 51, has been married to his wife, Pauletta, for 22 years.
A call by The Associated Press to the actor's representative wasn't immediately returned Tuesday.
Lathan stars in the upcoming romantic comedy "Something New."
Washington, who won Oscars for his roles in "Glory" and "Training Day," stars in Spike Lee's new film, "Inside Man."