The pair met when they starred together in the 2015 film Sky.
While they were promoting the movie, the 40-year-old actress admitted to being nervous about her intimate scenes with the Walking Dead star.
“We share a lot of intimate scenes. I was really nervous about meeting him and not being able to have a drink with him, or talk with him,” she told People.
But she admitted she was “pleasantly surprised” with Reedus, 48, and that he is very different from the characters he plays onscreen.
“He’s so relaxed. He’s really easygoing, very gentle.”
Diane, 40, split with boyfriend of 10-years Joshua Jackson back in July 2016.