A Denton County grand jury Thursday indicted "Girl in the Closet" Lauren Kavanaugh on three counts of sexual assault of a child after she admitted sexually assaulting a 14-year-old girl.

Lauren Kavanaugh (Denton County Sheriff's Department)

A sexually explicit Facebook conversation led police to question Kavanaugh and approach the girl's family about the allegations. The girl and Kavanaugh met through a Facebook fan page called "The Lauren Kavanaugh Story" that has since been disabled.

Kavanaugh, 25, faces up to 20 years in prison on each charge if she is convicted. She has remained behind bars at the Denton County Jail since her December arrest.

As a child, Kavanaugh was the victim of horrific abuse at the hands of her mother and stepfather, who locked her in a filthy closet in their Hutchins trailer. The Dallas Morning News told her story in an eight-part series titled "The Girl in the Closet."

Her mother and stepfather, Barbara and Kenneth Atkinson, are serving life sentences in Texas prisons. They are eligible for parole in 2031.

Kavanaugh's attorney declined to comment Thursday night.

Lewisville police learned of the Facebook conversations in December after the social media company contacted the National Center for Missing and Exploited Children. Facebook's monitoring software detected a suspicious interaction between an adult and child. The center reported the possible crime to Lewisville police.

Lewisville police Detective Bryan Gibbins wrote in the arrest warrant affidavit that he contacted the teen's mother Dec. 17 about the online conversations and asked her to bring her daughter to the Denton County Children's Advocacy Center for an interview, court records show.

The records don't indicate when Kavanaugh and the girl began communicating -- first on Facebook and then via text. But they stopped talking in October 2017 when Kavanaugh moved, according to an arrest warrant affidavit.

But last year, Kavanaugh returned to North Texas, reconnected with the girl and moved in with her family, the affidavit says. They lived in an extended stay motel in Lewisville.

The girl detailed sex acts between her and Kavanaugh, including the night before Kavanaugh's Dec. 17 arrest, according to the affidavit.

On the same day the girl was interviewed at the Children's Advocacy Center, Gibbins went to the motel, told Kavanaugh he was a police officer and asked if she would talk with him at the police station, the affidavit says. She agreed.

At first, Kavanaugh told Gibbins that she and the girl were "just friends," the affidavit says.

Then, Gibbins told her that he had a transcript of their sexually explicit chat.

"I asked Lauren if that was true and after sitting quietly for a while, Lauren looked up at me and said 'yes,'" Gibbins wrote in the arrest warrant affidavit. "Lauren also said that was the only time and that she was sorry and learned her lesson."

He then asked Kavanaugh whether there were other times she and the girl were "involved sexually," and she became upset.

"If you're going to arrest me, arrest me!" she responded, according to the affidavit.

Kavanaugh then said she didn't want to talk anymore.