Asked if she had been drinking, Osborne said no and the strong smell the principal sensed was just mouthwash.
"While looking to locate the mouthwash, the principal saw a water bottle in Osborne's laptop bag which was about one-third full," the decision said.
After brushing past the principal and spilling the contents down the drain, Osborne turned the tap on and tried to fill the bottle.
"The Principal smelt the remaining contents of the bottle and detected a distinct smell of alcohol," the decision continued.
"When asked, Osborne said there was water in the bottle and maintained she had not consumed alcohol."
However, the former teacher changed her tune the next day.
Osborne sent an email to the principal acknowledging she had bought alcohol and apologised for having it on her person at school.
Later in the day, she confirmed she had consumed alcohol before resigning from her job the next day.
Her case was referred to the Complaints Assessment Committee of the Teaching Council, who charged her with serious misconduct in the Disciplinary Tribunal.
Osborne did not dispute the claims about misconduct and it was found the act brought the profession into disrepute.
"The Tribunal considered that Ms Osborne has taken steps towards her rehabilitation and thought transparency was an important factor in deterrence for her," the decision said.
"Osborne was censured and had conditions imposed on her practising certificate to provide the Teaching Council with updates on rehabilitative steps every three months for one year and to disclose the decision to employers for two years."