LeAnn Rimes Attempts to Shut Up Eddie Cibrian's Ex

Sources close to Brandi Glanville and the country songstress' beau reveal an impending lawsuit between the two

It seems a little late in the game for ceasing and desisting of any kind, but that's not stopping LeAnn Rimes.

A source close to Rimes' soon-to-be divorced beau, Eddie Cibrian, tells E! News exclusively that the country songbird's lawyers sent a cease and desist letter to his estranged missus, Brandi Glanville, Thursday citing allegations of slander. Should Cibrian's ex not respond to the note in five days, the letter stated, Rimes will move forward with a lawsuit.

Reliable Glanville sources, however, deny any wrongdoing on her part...

"Brandi has been nothing but nice to LeAnn," says the source. "She let her kids go to Mexico with them, and she is genuinely happy that they like her. If they didn't, then she would be upset."

In recent months, things have been relatively quiet on the rocky Rimes-Cibrian-Glanville front, which makes news of a out-of-the-blue cease and desist letter all the more shocking.

Apparently, according to the source, Rimes' slander allegations stem from before Eddie and Brandi even split. Around that time, Glanville reportedly told the press Rimes was "stalking" her then-husband, but as the source explains, she was unaware of the Lifetime movie costars' affair, and only made those statements before Cibrian broke the news to her.

In response to Glanville's denial of anything slanderous, a source from Rimes' camp reveals to E! News that the letter was indeed sent, and comes "after months and months of Brandi speaking about LeAnn in the press and telling lies. This is a reaction, and something she felt was necessary to do to protect herself,"

Rep for both Glanville and Rimes had "no comment" on the claims, still, sources close to the now-single mom tell E! News her attorneys plan on responding to the letter in the coming days.

Meanwhile, according to our source, Glanville and Cibrian's divorce is close to be official.