The actress, who plays Gillian Foster, told TVLine that the pair's teasing of each other could be a mask for their true feelings.
"I think they joke around a lot, and yet there's truth within those jokes," she suggested. "It's certainly fun to play those scenes with Tim!"
However, she claimed that the show could suffer if Lightman and Foster were to become an official couple.
"Let's say they do love each other and that comes to fruition," she said. "Well, then what? Then they have a regular relationship? Do we watch television for regular relationships?"
The third season of Lie To Me was recently cut to thirteen episodes when Fox declined to order nine further instalments.
The series continues on Mondays at 8/7c.