Story highlights Deborah Bradley made the admission in an interview with NBC

She says she last saw Lisa four hours earlier than the time initially given

Bradley says police have accused her of killing her daughter

The mother of Lisa Irwin, an 11-month old Missouri girl missing for nearly two weeks, said in an interview she was drunk the night the infant disappeared.

Deborah Bradley made the admission during an NBC interview, portions of which were aired Monday on "Today."

She also said she last saw Lisa at 6:40 p.m. October 3, when she put the girl to bed, not at 10:30 p.m., as initially believed.

Lisa was reported missing at 4 a.m. October 4, after Lisa's father, Jeremy Irwin, came home from work to find the door unlocked, lights on and a window that had been tampered with at the family's Kansas City home.

Bradley told NBC she is afraid she will be arrested. Police have accused her of killing Lisa, she said, and told her that she failed a lie detector test, with deception indicated when she was asked where Lisa was.

"I was the last one with her," a tearful Bradley said in the interview. "And from judging on how the questioning went, that's kind of a fear that I have. And the main fear with that is, if they arrest me, people are going to stop looking for her. And then I'll never see her again, and I'll never know what happened."

Asked how much she had been drinking that night, Bradley said, "enough to be drunk."

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But she rejected the notion that she could have harmed her daughter while under the influence of alcohol.

"No, no, no," she told NBC. "And if I thought there was a chance, I'd say it. No. No. I don't think alcohol changes a person enough to do something like that."

She said it's "terrible" that police may be focusing on her. "My daughter is missing," she said. "The last thing that I want to have to worry about is something like that. I shouldn't have to put any energy, any time or effort, into anything but finding her."

Asked whether he had questions about Bradley, Irwin told NBC, "No. There's no question to be had there. I know who she is. I know the kind of mother she is."

He said it's possible someone could have entered the house without Bradley hearing, as the couple's bedroom is on the opposite corner of the house from Lisa's room and Bradley sleeps with a fan at high speed.

Police have said three cell phones were also missing from the home along with Lisa.

On Sunday, Missouri Gov. Jay Nixon ordered the one-day deployment of 25 National Guardsmen to help search for Lisa.

Two anonymous benefactors have offered a $100,000 reward for Lisa's safe return, according to Bill Stanton, a private investigator working with the family.

Irwin and Bradley told NBC they have refused to let authorities re-interview Lisa's older brothers.

"They said they heard noises (the night Lisa disappeared)," Bradley said. "I don't know if that was before we went to sleep or after." She said she has not talked to her sons about it because she is reluctant to put them through "anything else."

Asked what she would say to someone who might be holding Lisa, Bradley told NBC, "She needs her family, and we need her. We're losing more sanity as each day progresses."

Lisa is described as being 30 inches tall with blue eyes and blond hair, according to police. She weighs between 26 and 30 pounds and was last seen wearing purple shorts and a purple shirt with white kittens on it.

The missing girl has two bottom teeth and a "beauty mark" on her right outer thigh, police said. At the time of her disappearance, she had a cold with a cough.