Along the way, Cross not only spent countless hours in front of a computer screen creating dialogue and camera directions, she also found herself in countless courtrooms fighting off vultures who swooped down to suck the life out of her intellectual property.
One of the four lawsuits she filed in Europe was against a plagiaristic production company.
"It was outrageous," Cross said. "They stole not only characters and scenes from my novel but even dialogue. You'd think they'd try harder to disguise their theft."
It took her nearly two years and $80,000 to win that suit, and three more legal battles consumed more time and money.
"So, contrary to what most people think," Cross said, "I not only didn't make money, I was out of pocket for this film for a long time."
Even co-star John Goodman felt the sting of litigiousness as a "Pope Joan" producer sued him in 2007 for reneging on his commitment to play Pope Sergius. They settled out of court, but not before the production stalled. Then a director was fired for comments he made to the press. Then star Franka Potente ("The Bourne Identity") dropped out.
"It was a long, tortuous road I had to travel to bring my novel to the silver screen," Cross said last week. But that long, tortuous road has clearly taken a turn for the better.
After Potente forsook the title role, Goodman returned to the cast, Potente was replaced, and a bona fide British hunk was hired as Joan's romantic interest.
Since the movie premiered in Berlin in October 2009, the book is selling well again, buoyed by Cross's endless lecture tours, book-club phone chats and indefatigable Internet efforts.
The two-and-a-half-hour English-language movie - favorably compared to such historical spectacles as "Quo Vadis" - follows Joan's struggles through Norse invasions and the sacking of Rome. In modern-day Morocco, Wortmann vividly recreated the Eternal City of the Middle Ages and populated it with bazaar vendors, tooth-pullers, soothsayers, acrobats, pigs, goats and horses.