Lady Gaga's "childish diva" behavior doesn't fly with one of the industry's most notorious hot heads, Vogue's editor-in-chief Anna Wintour, and RadarOnline.com has all the details.

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According to Maureen Callahan, author of the much-anticipated biography Poker Face: The Rise and Rise of Lady Gaga, the eight-time VMA winner performed in May at Wintour's Metropolitan Museum Costume Institute Gala, and the two did not get along.

There's about to be a lot revealed about Lady Gaga in a new blockbuster biography about the Bad Romance singer that hits shelves on Tuesday, September 14 - and only RadarOnline.com has exclusive excerpts before the book's release.

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Among the many interesting things about Gaga in Poker Face: The Rise and Rise of Lady Gaga is why she canceled her headlining tour with Kanye West last summer.

"He's a grade-A disaster, a mess. If his name is on it, no one will touch it," a source inside West's camp told author Maureen Callahan.

Lady Gaga’s bad romance with an ex lover and disgruntled music producer is over.

Songwriter and music producer Rob Fusari — who claims he helped launch Lady Gaga's career — dropped a $30.5 million lawsuit against the pop superstar, RadarOnline.com has learned.

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In turn, the Grammy Award-winning Poker Face singer called off her dueling lawsuit against him, which was filed in March.

Read the court papers here.

It’s unclear if the pair struck a monetary settlement as part of the apparent peace deal, but Fusari had previously alleged he was denied a 20 percent share of her song royalties.

It turns out Lady Gaga’s love life is just as controversial as her outrageous stage costumes.

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The blockbuster biography Poker Face: The Rise and Rise of Lady Gaga – set to release next week – details a romantic relationship Gaga had with her former producer Rob Fusari and RadarOnline.com has all the exclusive details.

According to the book authored by Maureen Callahan, Fusari pressured Gaga into having a relationship with him even though he was living with his fiancé at the time.

EXCLUSIVE PHOTOS: Lady Gaga Before She Was Famous – Together With Rob Fusari

Friends of Gaga are quoted in the book saying Fusari took advantage of her and she eventually fell in love with him.

The couple has since broken up and Fusari has slapped Gaga with a $30.5 million lawsuit, claiming he gave her the name Lady Gaga and owns a 20 percent share of her career.

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Fusari was the co-executive producer on Gaga’s debut album The Fame and co-wrote four songs including the smash hit Paparazzi.

Also exposed in the book is the revelation that Gaga’s father Joe Germanotta is half-owner in her business.

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Industry executives and lawyers interviewed in the biography say it is almost unheard of for an artist to share half their business with anyone and that Gaga often gets into arguments with her father over her frivolous spending.

When contacted by RadarOnline.com, Gaga’s rep and father were unavailable for comment.

Born Stefani Germanotta, she has evolved into the most iconic pop star of the 21st century known as Lady Gaga, but some people are stepping forward to claim her image is a hoax.

In Maureen Callahan’s much-anticipated tell-all book, Poker Face: The Rise and Rise of Lady Gaga, former classmates knock Gaga, saying she was not the “freak” she says she was but that she was “normal.”

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“When she says in interviews, ‘I live and breathe fashion’ – she may be fooling other people, but she’s not fooling me,” said Jon Sheldrick who knew Gaga when she attended New York University.

“I don’t mean to sound demeaning, but she was really normal. She wasn’t super-outspoken or into really edgy clothes. She was wearing T-shirts and sweatpants and sh*t. She was not a misfit.”

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The book goes on to describe Gaga as a “fresh-faced girl, perpetually smiling, surrounded by other, perpetually smiling young girls” during her years at Covent of the Sacred Heart, an exclusive all-girls Catholic school also attended by Paris and Nicky Hilton.

“I’m a friend of hers on Facebook still; she still has her original profile up. She only has, like, four hundred friends,” said Seth Kallen, fellow musician at NYU.