City News Services reports the woman, whose name was not immediately released, was arrested early Monday for investigation of child abandonment.
Police say a restaurant employee saw the child sitting alone in a stroller about 2:30 a.m. The worker estimates he watched the girl sit there alone at least 15 minutes before calling police.
The mother did return, police say, and that's when she was arrested.
The girl was taken to a hospital and didn't appear to have any injuries. She is expected to be placed in protective custody.