Speaking to Smith on her Facebook show Red Table Talk, the actress said that the relationship happened while the pair were separated.
"We were over," she says. "From there, as time went on, I got into a different kind of entanglement with August."
Mr Smith then presses her, saying "an entanglement? A relationship."
"I was in a lot of pain and I was very broken," she countered.
The pair have been married since 1997, have two children together, and said they are currently back together after a split.