Paula Deen’s longtime powerhouse publicist, Nancy Assuncao, has quit after six years over the butter-loving chef’s plan to plug a diabetes drug.

Assuncao faithfully stuck with Deen through years of hearty drama, including her battle with rival chef Anthony Bourdain, who called her “the most dangerous woman in America.” But she quit as Deen’s spokeswoman and chief marketer last month as Deen negotiated her deal to hawk the drug Victoza.

Deen, now under siege by diabetics, nutritionists and fellow chefs for keeping her own Type 2 diabetes secret for three years, even as she pushed recipes full of sugar and fat, probably could use Assuncao’s help now. Deen only revealed her diagnosis last week.

A source said Assuncao “strongly disagreed with Deen’s dramatic turnabout, after years of promoting fatty foods, to announcing she has a deal with a diabetes drug company [Novo Nordisk] and will be promoting lighter food and ‘diabetes in a new light.’

“While Paula did tell some people at her live appearances about her diabetes, she certainly didn’t talk about it on her show. Nancy disagreed with Paula’s plan to be a drug-company spokesman and challenged her decision. But this wasn’t a battle Nancy felt she was going to win. She couldn’t be part of it.”

Assuncao, whose past clients have included Ian Schrager, told us last night, “I’m very grateful for the six years that I worked with Paula in helping her build the Deen brand.

“Although we had a great deal of fun along the way, I could not agree with the new business strategy going forward. Nonetheless, I wish them continued success.”

Deen’s new rep could not be reached last night, with a staffer at her office telling us, “She is on the Paula Deen cruise.” The chef’s Web site said Celebrity Cruises’ Eclipse would be a “tasty journey” in the Caribbean with a group buffet dinner, a cooking demo and a personal photo with Deen (one per family).