In a not-so-surprising move, Gruner + Jahr USA Publishing on Tuesday filed a breach of contract lawsuit against Rosie O'Donnell, charging that the onetime warm and fuzzy TV personality radically changed her public persona and helped to scuttle her 18-month-old, on-the-road-to-being-successful namesake magazine.

G+J is asking for $300 million from O'Donnell and her production company, Lucky Charms Entertainment, Inc., according to the suit, filed in Manhattan State Supreme Court.

O'Donnell's spokeswoman, Cindi Berger, told New York's Daily News that O'Donnell, 40, will "aggressively" defend herself and will countersue. "Her name and integrity are at stake," said Berger.

According to the suit, the relationship between G+J and O'Donnell "changed drastically beginning in July 2002, when O'Donnell, having recently terminated her daytime television talk show, began to transform her public persona from the warm, fun-loving 'Queen of Nice' to a self-proclaimed 'uber bitch,' and to behave erratically and in defiance of her contractual commitments to G+J."

The lawsuit also claims that O'Donnell said: "If I have to go down, I will take G+J down with me, even if I have to spend every last cent I have."

On Sept. 18, O'Donnell announced at a New York press conference that she was severing all ties with the publisher because Rosie magazine no longer represented her "vision and ideas."

A member of the Rosie magazine staff tells PEOPLE.com that on Thursday G+J intends to inform the publication's employees of the future of the magazine, if any. A December issue reportedly has just been sent to the printer.

Meanwhile, making light of the lawsuit, New York Post media columnist Keith Kelly has suggested that G+J quickly hire actress Rosie Perez or onetime gridiron great Rosey Grier to take over the title, or even TV host Charlie Rose.

Failing that, there's always former Cincinnati Reds star Pete Rose.

• For an exclusive interview with Rosie on the magazine shakeup, check out this week's PEOPLE cover story.