In her new memoir, "If We Break: A Memoir of Marriage, Addiction, and Healing," Hunter Biden's ex-wife Kathleen Buhle detailed her early relationship with her former husband and their divorce, saying her daughters found out about his affair with his brother Beau's widow after finding his phone. 

According to an excerpt of Buhle's book, her daughters discovered text messages on their father's phone with Hallie Biden, Beau's widow. Buhle drove to their therapist's house after receiving a distressed call from one daughter, asking her to come there. 

With one daughter there and one on speakerphone, their therapist, Debbie, was asked to break the news to Buhle about the affair. "Can you tell her? We can't do it," one daughter said to Debbie, according to an excerpt of the memoir published in People magazine.

Buhle wrote that Debbie looked her in the eye and said, "Hunter's having an affair with Hallie." She described watching her daughter's face relax after they told her the news. 

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Hunter Biden

Kathleen Buhle, the ex-wife of Hunter Biden, detailed her divorce and finding out about his affair with his sister-in-law in a new book. (Teresa Kroeger/Getty Images)

"If anything, I felt a strange vindication. Not only had I not been crazy, but it was so much worse than I could have imagined. I was shocked, but not heartbroken. Heartbreak had already flattened my self-esteem that past year," Buhle said, according to the excerpt. Debbie told Buhle that they had called Hunter and told him that they knew about the affair.

Buhle said that it was a "relief" that there were "no more secrets." 

She also detailed the relationship between the two following the death of Beau. Hunter spent a lot of time with Hallie after the funeral, she wrote. 

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Hunter Biden and Joe Biden

Hunter Biden's ex-wife detailed how she heard about the affair between Biden and his brother's widow Hallie in her new memoir. (Reuters/Joshua Roberts)

After Buhle found a crack pipe in an ashtray, she made Hunter move out. She detailed her "own kind of addiction," which consisted of watching Biden's every move in terms of credit card charges. He told her that he was "healthy and sober." 

"I didn't want to admit, to myself or anyone else, how unhealthy our relationship had become, so my struggle was just one more secret," Buhle wrote.

People asked her about the "Justice Department investigation into his finances and business affairs" and Buhle said, "Whether or not I'm questioned, I couldn't be of any help…I kept my head so deeply buried in the sand on our finances."

In the memoir she wrote, "He started many ventures . . . a real estate investment fund and then a technology company. I didn't understand any of it, or what pieces of his businesses actually generated income for us. I worried that we lived above our means, but I did nothing to change it. The way that Hunter and I handled money was that whenever I needed any, I called Hunter. More than once my debit card was declined at a store. I'd have to call Hunter to transfer money into my account. Hunter and I drove nice cars and had a beautiful home, but we were running fast on that hamster wheel and barely staying on."

Hunter Biden at Inauguration

Hunter Biden's daughters found out about his affair with sister-in-law Hallie Biden after finding his phone and seeing texts between them, according to Kathleen Buhle's new memoir. (Greg Nash/The Hill//Bloomberg via Getty Images)

Biden's ex-wife also wrote that following Joe Biden and Barack Obama's victory in 2008, a Secret Service agent visited their home and said that Hunter and their three daughters would have Secret Service details assigned to them. Buhle, however, did not have agents assigned to her, which she said felt like "one frequent reminder I wasn't a true Biden."

When she first met Hunter, she said he tried to tell her that he came from a middle class family, the excerpt said. After going to his house, she told Hunter, "[A] kid from a middle class family does not have a ballroom."

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Following her divorce in 2017, Buhle was diagnosed with colon cancer; she is now four years cancer-free. 

Buhle's new memoir,"If We Break: A Memoir of Marriage, Addiction, and Healing," is set to be released on June 14.