Former Mistress To Take The Stand In Christie Brinkley-Peter Cook Divorce Case

NEW YORK, New York -- Two days before July 4, there will be equally explosive fireworks in a Central Islip, New York courthouse, where Christie Brinkley and Peter Cook are set to begin their divorce proceedings.

But it won't be just the two of them squaring off.

[ Christie Brinkley Divorce Details To Be Public - Play it Now ]

Diana Bianchi, the then-teenager whose affair with her boss (Cook) caused the rift between Brinkley and her husband, is slated to testify the very first day of the case, her attorney Rosemarie Arnold told Access Hollywood exclusively.

Arnold, whose client was subpoenaed a couple of weeks ago, says Bianchi is "not looking forward to testifying and getting involved in this dispute," but added, that "if compelled to testify, she will tell the truth."

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That couldn't be worse news for Cook, who not only lost a bid last week to keep the proceedings private, but also because he reportedly paid Bianchi $300,000 to never talk about their headline-making affair in exchange for her not suing him for sexual harassment.

A source confirmed to Access Hollywood that a deal was made before a lawsuit was ever filed. Arnold, however, wouldn't comment on reports about any alleged hush money. Instead, all she said was that "the matter was resolved."

[ All Access: Divorces - Christie Brinkley - Celebrity Scandals - Courts ]

Access Hollywood has also learned that the one saving grace for Cook is that there is a very good chance that, other than confirming some basic details like her name and age, Bianchi is going to plead the Fifth Amendment and not answer questions about her illicit affair with Brinkley's husband.

Last week, Access Hollywood broke the news that among the embarrassing allegations that might come out during the divorce proceedings is that Cook allegedly trolled swingers sites in search of women.

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