(CNN) Elizabeth Thomas, the Tennessee teenager allegedly kidnapped by her teacher, was withdrawn and thinner after she was rescued, family members said Monday.

"She didn't look like herself at all. She looked like she was very worn out, very thin. And very jittery," her father Anthony Thomas said on "Primetime Justice with Ashleigh Banfield" on HLN. "She's somebody who's actually more sure of herself, usually all smiles and she's been sort of the life of the party."

Thomas and Elizabeth's older sister, Kat Bozeman, spoke with Banfield about the teenager's recovery. The 15-year-old high school freshman is apprehensive about being around people, said family members, who have kept conversations light and not peppered her with questions about her 39-day ordeal as she tries to heal.

Last week, authorities found the teenager in Northern California and arrested her forensics teacher, Tad Cummins, 50. A federal judge in California on Monday approved a request to transfer Cummins back to Tennessee, where he will face charges of kidnapping the teenage girl.

'Poor excuse for a human being'

Cummins is charged with transportation of a minor across state lines for the purpose of criminal sexual intercourse. The charge carries a minimum of prison term of 10 years and a maximum of life.

Cummins admitted he had gotten a small watercraft and conducted a test run from San Diego to Mexico, where he planned to take the teenager, according to a federal complaint.

Anthony Thomas called Cummins "a very poor excuse for a teacher and authority figure, a father .... he's a poor excuse for a human being," reacting to an interview with Cummins' sister defending her brother's actions. In the interview with NBC's "Today" show, she said her brother said Elizabeth wanted to run away and he didn't want her to go alone and went with her to make sure she was safe.

In an earlier interview Monday with CNN, Elizabeth's sister-in-law, Danielle Thomas, said Elizabeth may have thought she and Cummins were going on a one-day excursion and didn't anticipate leaving for more than a month and traveling more than 2,000 miles away.

"Number one, she didn't pack that many clothes," Danielle Thomas said. "Number two, she left her dog behind. And number three ... she is very active in her youngest sister Rebecca's life. So much so, that Rebecca would call her mommy. So, in my heart I don't think she would have left Rebecca for a very long time."

Danielle Thomas said the family's first inclination when Elizabeth went missing was that she had run away. But the family immediately realized what had taken place when Cummins' wife called and told them he was also missing.

"Immediately you get ticked off because some perverted old man has absconded with a member of your family. And then, there were times when we were upset at both, and then just at him. And then we were emotional," she said.

Family members said Elizabeth, one of 10 children, was recuperating at an undisclosed location, where she will undergo counseling and ease back to normalcy.

"Right now, she's somewhere where she can relax and be looked after by family and close friends and just take a break from everybody," Anthony Thomas said. "We can't just .... throw her right back in there and tell her to go clean her room."

'She's very withdrawn'

Bozeman said: "We're trying to keep everything light so she can heal."

Anthony Thomas and Bozeman, who were speaking from Columbia, Tennessee, said the teenager's weight loss is noticeable.

"This child loves food and she loves coffee," Bozeman said, adding that her sister is happy to "eat real food."

But the difference was also noticeable in the expression in his daughter's face, Anthony Thomas said.

"She is the only extrovert in an introvert family and she's very withdrawn," Bozeman said.

Danielle Thomas insisted that Elizabeth was still the jovial and playful teenager, who had peanut butter fights with her siblings in the middle of the kitchen. But when asked if the teenager was OK, Danielle Thomas said no, and shook her head.

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"There are times where you think she's OK and there are times where she's curled up in the middle of the floor crying and shaking and having panic attacks," Danielle Thomas said.

Anthony Thomas said he hasn't thought about the weight of a possible trial and that his daughter may have to face her alleged abductor in court.

"It's a day by day thing," he said.

"We've gone through probably the worst experience of my life so far was having her gone, not knowing where she was or how she was," her father said. "There's a lot still to go through."

He added: "But at least, we've got her back and that's the important thing and we can start moving ahead."