Debra Opri's lawsuit, filed Monday, accuses Birkhead of falsely claiming in a CNN interview she was a source for "Blonde Ambition: The Untold Story Behind Anna Nicole Smith's Death."
The book, by journalist Rita Cosby, claims Birkhead worked with Howard K. Stern, Smith's lawyer and sometime boyfriend, to manipulate the media and maximize profits after Smith died.
Opri denies providing information to Cosby. She contends his defamatory remarks were "planned and malicious."
The lawsuit claims defamation, fraud and other allegations, and seeks damages, including about $200,000 Opri says she spent to hire a crisis management firm to "salvage" her reputation. It was filed Monday in Los Angeles Superior Court, she said.
In December, a Los Angeles judge ruled in Birkhead's favor in the paternity case and a DNA test later revealed that he was the father of Smith's daughter.