Ah, but there's the rub. You know what the passenger had on the plane. What you don't know is how much they consumed in the bar prior to boarding. (And, as a flight attendant who works F/C a lot, this is becoming an increasing problem on a number of flights. I recently had a passenger who had one drink after takeoff, and when he tried to order a second drink he was slurring so badly that at first I thought he was ill--like a stroke.) Unless this was a case of alcohol/drug interaction (which does not excuse her behavior), I'm betting she started celebrating her trip long before she boarded.