McMillan, 55, filed the complaint Wednesday in Contra Costa County Superior Court against Jonathan Plummer, 32, who inspired her best-selling 1996 novel, "How Stella Got Her Groove Back." The book, later adapted into a movie starring Angela Bassett and Taye Diggs, chronicled the adventures of a 40-something woman who falls for a guy half her age.
The lawsuit claims Plummer, a Jamaica native, married McMillan in 1998 only to become a U.S. citizen. He later announced that he is gay.
The couple eventually settled their divorce for an undisclosed amount.
Plummer's lawyer, Dolores Sargent, also is named in the lawsuit.
"The defendants conspired and formed a plan to threaten to humiliate and embarrass Terry McMillan," the lawsuit said, "and violate her privacy and place her in harm's way, and threatened to damage her professional and personal standing in an attempt to extort monies from her."
McMillan's allegations include emotional distress, invasion of privacy and placing her in a "false light" to harm her professionally and personally. She also claimed that Plummer violated a restraining order by calling her to speak with her son.
Plummer, now a Danville hairstylist, declined to discuss the lawsuit Wednesday. Sargent could not be reached for comment.
One of McMillan's attorneys, Daniel Horowitz, declined to comment on the case.
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969