A police investigation was launched after a complaint on Feb. 16, 2012, that one worker was taken to hospital after eating lunch.
Later, tests showed an antipsychotic drug was added to the food.
Police say there were also multiple incidents between April 1 and Dec. 31, 2011.
The woman, who works at a financial institution, was later arrested and charged with two counts of administering a noxious substance.
She was scheduled to appear in court Tuesday.
The charges could lead to a jail term of up to two years.