Siobhan Houston (25) was visiting a prisoner when she was caught with 5.5 grams of the drug.
Appearing at Falkirk Sheriff Court last Thursday, Houston pled guilty to attempting to take the class B drug into the YOI on November 30.
Sheriff Derek Livingston said: “Attempting to take drugs into a prison is high up in the level of offences.”
He deferred sentence on Houston, 5 Lochiel Lane, Rutherglen, until January 19 and called for a restriction of liberty order assessment to be carried out.
Back in August mounted police officers were part of a team carrying out checks and searches of visitors to Polmont YOI. The aim of Operation Trossachs was to prevent, detect and disrupt those intent on smuggling drugs or other banned items into the prison.