A police spokesman told Nine News that the 29-year-old was arrested at a shopping centre in Ryde, in Sydney's north-west on December 22 after she began 'acting aggressively towards customers.' Police further allege that Ms Tyrrell continued to swear in the presence of multiple children, as well as spit in the face of one officer.
Ms Tyrrell was subsequently arrested and charged with assaulting an officer and using offensive language in a public place.
Ms Tyrrell's three-year-old son William vanished while in the care of foster grandmother in Kendall, NSW on September 12, 2014.
He was reportedly playing hide-and-seek in the garden at the time of his disappearance.
Police have never suggested that William's biological parents or foster families were involved in his disappearance or are at fault in any way.
The investigation of William Tyrrell's disappearance is still active, and there is a $1 million reward with information leading to the recovery of William.