Basically what I figured. They both go out, get smashed, and bust company rules on alcohol consumption. They get caught, he comes clean to the company, and they get deadheaded back which is bad, but not as bad as showing up to the airplane in violation. Because Pina is on probation, she comes up with this "I was drugged" story to save her ass.
Occams razor at work, in order to believe the drugging, you would have to make a bunch of assumptions to get there, while the story that they were both drinking, got drunk off their asses, violated company policy on alcohol, and then, because she is on probation, this drugging story was concocted to keep her job makes the most sense.
Now their behavior while they were smashed still needs to be investigated in regards to inappropriate hehavior, but the idea that she was drugged will be tossed unless she can come up with a some kind of solid evidence.