Vanessa Williams Talks Childhood Sexual Abuse in 'Nightline' Interview

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Vanessa Williams opens up about some long-hidden secrets in an interview with ABC's Nightline on Tuesday.

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First, she was molested at 10 years old by an 18-year-old girl during a trip to visit family friends. She writes about the encounter in a new memoir, titled You Have No Idea, which made headlines earlier this month with the revelation of Williams' abuse.

"It was definitely a choice, because it didn't need to be [in the book]," the Desperate Housewives actress tells Nightline. "It happened one night where she told me, 'come over here,'… I didn't know that it was wrong, but I knew that it wasn't right because I wasn't supposed to tell anybody."

She did not fully grasp the weight of the incident until college, but it affected her growing up: she rebelled, and pulled away from her parents.

"I think I was highly sexualized because I was in fifth grade and I had this experience," Williams says. "Because it feels good, you're like, OK, well this is supposed to be normal. That's not normal for a 10-year-old to be seduced."

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Williams' memoir arrives Tuesday. You Have No Idea: A Famous Daughter, Her No-nonsense Mother, and How They Survived Pageants, Hollywood, Love, Loss (and Each Other) is co-authored by Williams' mother, Helen Williams, who joins her in the Nightline sitdown, slated to air at 11:35 p.m. ET.

"[I] had no idea that, that had happened," she says of her daughter's experience. "But in retrospect, it kind of put into place some of her reactions during her pre-teen years."

Williams, 49, became pregnant in high school and had an abortion, which she kept secret. "Being pregnant is the most frightening thing that happens in your life," she says. "I knew in high school that's something that I was not prepared to do, or fight, or struggle with."

Williams has four children: three from her first marriage to manager Ramon Hervey II and one from her marriage to ex-NBA star Rick Fox.

Another intriguing detail: Williams, Miss America 1983, received death threats and massive security protection as the first black woman to win the crown. Sharpshooters were often at their marks on buildings during her public appearances.

"[My mother] wouldn't discuss them with me, because she didn't want me to be freaked out by them the entire year while I was doing my appearances," she says.