REALITY TV train-wreck Brandi Glanville has hit rock bottom – to the delight of her deadly rival LeAnn Rimes!

“The Real Housewives of Beverly Hills” star is filming “Celebrity Apprentice” in a bid to boost her popularity after a series of ugly public blunders, but it’s been a disaster.

“Brandi is acting really erratically,” said an insider. “She’s constantly arguing with her co-stars, especially Kate Gosselin. Producers have told her to pull herself together, but it’s not looking good.”

Another source says that Brandi has resorted to boozing and taking Xanax to deal with the pressure, all of which amuses LeAnn to no end.

Leann is like a cat that ate the canary right now,” a source close to the country songbird, 31, told The ENQUIRER. “Brandi has gone out of her way to bring LeAnn down in the past, so it’s no exaggeration to say LeAnn loves hearing that she’s self-destructing so spectacularly.”

The pair’s feud started in 2009 when actor Eddie Cibrian, 40, famously cheated on then-wife Brandi with LeAnn. The “Blue” singer eventually left her spouse of seven years, backup dancer Dean Sheremet, and married Cibrian.

Since then, the two women have savaged each other’s character on Twitter and in numerous interviews, and repeatedly butted heads over the welfare of Cibrian’s sons – Mason, 10, and Jake, 7.

Brandi’s reputation took a hit in January when she tastelessly joked that she’d “wanted to be mo­lested” as a child. She’s also come under fire for allegedly insensitive remarks about race and openly admits her boozing has spiraled out of control.

Fed up “Housewives” fans started a petition to get Brandi booted from the show, and her cast mates have criticized her.

“Brandi thought competing on ‘Celebrity Apprentice’ would improve her image and she could reinvent herself,” said another source. “Instead, it’s been a nightmare. And topping it off, she knows LeAnn is loving every moment of her demise.”