Righetti's character Grace van Pelt had been dating Wayne Rigsby (Owain Yeoman) but the pair were forced to split up in the last season.
"They're skirting around the idea," Righetti told TV Guide. "They're pretending that they're OK with the fact that they're not dating anymore, but they're not OK with it."
She added: "I was sad they weren't together longer. There's something about his protectiveness with her that I think is really charming."
The Mentalist returns for a new season on September 23 on CBS.