EXCLUSIVE

O.G. 'Apprentice' bitch Omarosa Manigault isn't about to let some ‘Real Housewife' from Down Under rip-off her self-help book -- and now she's taking legal action to block the "bitch."

The ‘Apprentice’ vet served Pettifleur Berenger -- one of the "Real Housewives of Melbourne" -- with a cease-and-desist for her recent self-help book, "Switch the Bitch: My Formula to Being the Champion of Your Life, Not the Victim."

Sound familiar? Omarosa dropped her own motivational tome, "The Bitch Switch: Knowing How To Turn It On and Off" ... back in October of 2008.

Gotta say ... Omarosa and her lawyer, Bradford M. Cohen, fired off a pretty entertaining letter. They demand a full accounting of Berenger’s book sales … which they say “should not take long” -- since it's an "absolute bore to read."

Lastly, if Berenger doesn't pull her "literary classic" off shelves immediately ... Omarosa says she will file a lawsuit seeking $150k for each violation of her copyright.