After Rachel Jeffs broke free from the isolated polygamist cult that raised her, she “almost felt guilty for being happy.”

The daughter of Warren Jeffs, the self-proclaimed prophet of the secretive Fundamentalist Church of Jesus Christ of Latter Day Saints, Rachel originally had been sent off to live by herself as punishment by her father.

Her alleged crime: Having sex with her husband while she was pregnant, an act already forbidden by FLDS.

Rachel was forbidden from seeing any of her five children for seven months. That banishment became the breaking point that led her to flee the sect.

“I was very angry at Father, and I was angry that he would do that to my kids,” Rachel recalled Friday on Megyn Kelly TODAY, in her first live television interview. “And I feel like he was punishing me for what he did to me. Like he was trying to break me and make me feel like I was worse than him. I wouldn’t let myself go there. I knew he had done wrong, and I didn’t want to let him break me.”

Rachel had already been subjected to a childhood of sexual abuse from her father, who started molesting her “way more times than I could count” when she was 8. He also took her to bookstores to show her pornography.

Rachel Jeffs and her father Warren Jeffs. Rachel Jeffs

“It was so against his teachings, so against what he had taught us, I didn’t even know what to think. And I just felt terrible,” she told Kelly.

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In a series of interviews with Kelly that also will air Friday on "Dateline," Rachel recounted growing up inside the FLDS community on an isolated ranch, and how she escaped that life. Her harrowing experiences are also the basis of a new book, “Breaking Free.”

Rachel was her father’s first “plural” daughter, born to the second of more than 50 wives Warren had. When she was 10, Rachel told her mother about her father’s abuse because “it was getting so bad and I just felt like I couldn’t handle it anymore.”

Some of the dozens of wives of FLDS leader Warren Jeffs, whose portrait hangs from the background. TODAY

Her mother confronted Warren, but the molestation continued. Her mother never said another word, mainly because of an FLDS rule requiring women to “keep sweet.”

“That’s how we kept heavenly father’s spirit,” Rachel told Kelly.

Women could not get angry, jealous or show negative emotions, or risk being punished by Warren, their leader: “We were supposed to be submissive and sweet.”

Rachel said the abuse stopped when she was 16 after she wrote her father a letter telling him to stop.

Shortly after, Warren arranged for her to get married to a young man named Rich, who already had two wives. The couple met for the first time on the day before their wedding.

Rachel went on to have five children, but later was banished by her father, who by that point was behind bars.

After being put on the FBI’s Ten Most Wanted List for a list of sexual misconduct charges, Warren went to prison for abusing young women and forcing many of them into arranged marriages at ages as young as 12. But he continued to lead his community from prison, sending them edicts that became increasingly erratic. He put odd restrictions on what his followers could wear or eat.

“And then he started sending really harsh punishments over assumed wrongs that they never committed,” Rachel said.

That’s when she was sent away for allegedly having sex with her husband.

Through a complicated journey, Rachel, her children, and a sister eventually fled the compound with the help of her grandparents and other relatives not affiliated with FLDS.

The freedom she soon experienced nearly overwhelmed her.

“Happiness had been pressed down so hard. It was so against our way of life that I almost felt guilty to be happy,” she told Kelly. “I was just happy to do what I wanted. It felt so amazing and I realized the worth of freedom.”

Rachel now gives violin lessons for a living and continues to raise her children with her second husband — another former FLDS member who fled the community, and “a real friend.”

Rachel Jeffs at her second wedding, to a man who also fled FLDS. TODAY

Rachel hopes her story will inspire other women who may be experiencing turmoil in their lives.

“No matter what situation they’re in, know that they can be strong and use any hard experience, they’re going to make their life better and help others,” she said. “So often, if you help other people be happy, it helps you overcome your hardships and what you went through.”