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Grandma: Stephanie ‘was stupid’ to date CBS producer

“Late Show” staffer Stephanie Birkitt “was stupid” to ever go out with CBS News producer Robert “Joe” Halderman — who is now charged with shaking down David Letterman for $2 million by revealing the talk-show host’s affair with Birkitt, the staffer’s granny told The Post today.

“People make mistakes and that was one of hers,” Irene Boyle said of her granddaughter Birkitt’s long-term romantic relationship with the 51-year-old Halderman. “Joe was a mistake.”

Boyle, who turns 91 on Oct. 25, said, “I think she was stupid to go out with him.”

Boyle also said that Letterman “and Stephanie have always had a good relationship. They joked and kidded around.”

“They were just good friends,” Boyle said, speaking at the assisted living facility in Newport, NH, where she resides.

“She worked for Dave for 11 years. She said she never had sex with him.”

However, sources have identified Birkitt, 34, as one of several “Late Show” staffers whom the 62-year-old Letterman bedded over the years even as he was romantically involved for decades with Regina Lasko, whom he finally married last March.

Last Thursday, Letterman stunned his studio audience during a taping aired later that night by revealing he had sex with multiple staffers, and that he had been targeted by an extortionist who threatened to expose those trysts.

Earlier that day, Halderman had been arrested was identified as the alleged blackmailer of Letterman. He was freed the next day on $200,000 bond.

In early September, Haldeman allegedly kicked off the extortion scheme by leaving copies of Birkitt’s diaries, and the outline of a screenplay about a talk-show host’s cheating ways in Letterman’s limo.

Halderman had first learned last December from Birkitt’s diaries that she not only had sex with Letterman, but continued the affair even when she was living with Halderman in their Norwalk, Conn., home, The Post revealed today.

Boyle said that since the scandal broke last Thursday, her granddaughter Birkitt has gone into hiding and hired “a lawyer, just so she’s protected.”

Boyle also noted that her granddaughter “is very bright” and has herself passed the bar exams of New York and Connecticut.

Birkitt is a graduate of the Benjamin Cardozo School of Law.