A police officer tweeted to say the driver had been pulled over after being spotted driving erratically.
Drugs were also found in the car.
North Yorkshire Police traffic cop Mark Patterson tweeted: "This afternoon I assisted a response colleague in Scarborough by conducting a DrugWipeUK test on driver of vehicle which he had seen driving erratically.
"Positive test and drugs found in the car means one in custody. Not the Boxing Day evening she was planning."