A woman had gone to Ballymena Police Station in connection with another matter and police then found cannabis resin in her makeup bag.
Ashling Graham (39), of Beechwood Avenue in Ballymena, had the offence detected in August last year.
She admitted possessing a Class B drug.
Defence solicitor John Murphy said it was an “extremely small amount” which had been forgotten about.
At Ballymena Magistrates Court on January 10 the defendant was fined £100.