She let her out to use the bathroom and drove away, Assistant Police Chief Stephanie Smith of Caryville, Tenn., told the Knoxville News Sentinel. She said she just couldn't handle her anymore.
Lynn Cameron has cerebral palsy and is severely disabled, the Daily News reported.
Eva Cameron of Algonquin, Ill., the mother, is not expected to have any charges brought against her because her 19-year-old special-needs daughter is legally an adult, the paper's site Knoxnews.com said.
Aftee being tracked down, Eva Cameron gave Caryville police a statement explaining why she left her daughter in a Campbell County bar, Smith said.
The mentally disabled girl was dropped off at the bar on June 28, and was unable to provide authorities with her name, phone number or address, Knox News reported.
She had a 30- to 40-word vocabulary, Smith said.
The officer added that Lynn Cameron did not seem stressed when authorities arrived, but that her mother had no left her with any money, identification or extra clothing.
Police got a tip from an anonymous informant on Sunday and discovered Cameron's name, according to Knox News.
Smith said Eva Cameron is not legally responsible for her daughter, who has the mental capacity of a 2-year-old, because Lynn is over 18 and Cameron does not have legal guardianship of her.
Our district attorney said no criminal offense actually occurred, Smith said.
As terrible as it is, unfortunately there is nothing we can do, Smith told CNN. There is no doubt we need a law for mental health rights, but pending this investigation, we just don't know what else to do.
Smith said Cameron will not be returning to Tennessee. She said she was going to put it behind her, she said.
Eva Cameron told the Northwest Herald that she left her daughter in Tennessee because it has the, No. 1 health care system in the United States of America.
She basically said, 'I don't want her and I don't want to take her,' Smith told CNN.
The Northwest Herald reported that Cameron has another disabled daughter and was finding it difficult to take care of the two girls.
But authorities say Lynn Cameron is doing fantastic, according to the Daily Mail, and she will be taken to a facility where children and adults with disabilities are cared for.