The Lexington, Nebraska teacher accused of fleeing to Mexico and having sex with a 13-year-old former student last fall plead guilty Wednesday in federal court in Omaha.

Kelsey Peterson was a middle school teacher when she disappeared with Fernando Rodriguez last October. They were later found in Mexicali, Mexico. Shortly after the incident, Peterson was fired by the Lexington Public School District.

Peterson plead guilty of traveling across state lines with the intent of elicit sex with a minor, a felony. "She crossed the boundary, there's no question about that, that's why we're pleading guilty today," said Peterson’s attorney, James Martin Davis.

"It doesn't make any difference whether or not the male initiates it or the female initiates it, if someone is over a certain age and the younger person is under a certain age, then it's statutory rape. It's a strict liability statute."

The 26-year-old Peterson will be sentenced in September on a reduced federal charge of transporting a minor across state lines for the purpose of sex.

The charge does not carry a minimum sentence in federal prison, meaning she'll likely face around six-to-seven years in prison. The original charge, had she been convicted, would have carried a sentence of at least 10 years.

Peterson is not off the hook on state charges, which include kidnapping and first-degree sexual assault. Davis hopes those charges will be dropped.

It was a very emotional day for the Peterson family. When Kelsey first entered the courtroom, she waved to her parents and gave them a weak smile. Her mother responded with an "I love you" and then started crying.

Peterson's family left after the plea, but not before yelling at the U.S. prosecutor, asking him if he knew what he had done and calling him a liar. They also questioned Fernando's age, as does Davis. "All we've plead guilty (to) is the fact that he's under 18.”

"There is no proof that he is anything other than 14 years old now, there's no proof that he was anything other than 12 when this started," said immigration attorney Amy Peck.

Rodriguez is back in Nebraska with his parents. Peck is working to get citizenship for them. Unlike his two siblings, Rodriguez is not a legal U.S. citizen.

"He was brought here as a child, he did not choose to come to the states undocumented,” says Peck. “He was here, but this is the only home he knows and once here, he was not allowed to legalize under our laws so he should not be blamed for that."