Singer Leann Rimes during an interview with host Jay Leno on December 18 2012. Credit: Paul Drinkwater/NBC/NBCU Photo Bank

Remember that affair that LeAnn Rimes had with  Eddie Cibrian back in 2009? She's not done talking -- or singing -- about it!

Debuting a new song, "Borrowed," on The Tonight Show With Jay Leno, the country singer, 30, admitted to Jay Leno that "the song is about . . . the situation. I did go through a very public affair...with Eddie, who is now my wonderful husband."

Filming Lifetime movie Northern Lights, Rimes was married to Dean Sheremet when she fell for her sexy costar Cibrian, 39, then married to Brandi Glanville. "The song looks into the darker moments of things," Rimes explained.

"I call myself pathetic in the song because at that moment I was pathetic," she explained of lyrics in "Borrowed," which includes the chorus, "I don't want to give you back."

"A lot of people who have been in that situation can relate to kills me to give that up," she said. "It's a very intimate look into a very rough moment of my life."

Clad in a sexy black miniskirt and sheer top, Rimes also touched upon her recent stint in rehab for anxiety and stress ("The last four years have been very compressed with stress," she said) -- and her frequent nemesis Glanville, now a Real Housewives of Beverly Hills star.

"I should feel flattered that she thinks I'm so interesting that I can be a storyline in her show," Rimes quipped.