Zenaida Gonzalez, who is suing Casey Anthony for defamation, was arrested Friday night in Orange County.
Gonzalez, 41, was being held at the Orange County Jail on a charge of selling or giving liquor to someone younger than 21. She was arrested by the Florida Division of Alcoholic Beverages and Tobacco.
Gonzalez was in the process of posting bail, which was set at $250, early Saturday.
Anthony, who was found not guilty last year of murdering her 2-year-old daughter, Caylee, claimed that a baby sitter named Zenaida Gonzalez had kidnapped the girl.