Although she and Brandi Glanville have been locked in a brand-new war of words -- this time over Glanville's sons and Rimes' stepsons -- LeAnn Rimes isn't done rehashing how it all began with Eddie Cibrian.

Following Glanville's exclusive interview with Us Weekly's Rebecca Bienstock this week, Rimes, 30, is opening up once more about her infamous affair with Cibrian, 39, in an emotional interview special with E!'s Giuliana Rancic, airing Sunday, Dec. 9.

"Why act on it when you're both married and you both have families?" Rancic asks Rimes. (The singer fell in love with Cibrian while filming Northern Lights together in 2009. At the time, Cibrian was married to Glanville with sons Mason, 9, and Jake, 5, and Rimes was married to chef Dean Sheremet.)

"That is a huge question. I never, ever in my heart want to hurt anyone," Rimes says in the sit down. "But . . . I don't think anything can separate anything that's super-connected. You might have had so many wonderful things with each other's spouses in your relationship, but something along the way broke that. You can't break what's broken already."

Rimes then bursts into tears. Between sobs, she says, "No one . . . will ever understand how much thought and hurt, even towards each, other were put into our decision [to divorce our spouses and stay together]."

Despite their differences, Glanville, 40, told Us that she hopes to find a way to co-parent with Rimes and her ex.

"I have not, and do not, wish to engage in a battle fought through the media," she told Us. "My hope is that now that I have my ex-husband’s attention, I also can get his and his wife’s commitment to work with me to co-parent our children in a most loving, safe and supportive fashion." 

E! Special: LeAnn Rimes premieres Sunday, Dec. 9 at 8 p.m. EST on E!.