She hadn't previously got hangovers because she was never sober enough for the hangover to start.
yep, that much became clear to me too, but only becaue of a 24 hr period wher it was physically impossible to get alcohol. lots of things started to make sense at that point, and yes, most people can't tell if he's been drinking until he's had enough to bring down an elephant, and then he slides quickly into oblivion. I've had people marvel that someone can get so drunk so quickly on so little, not knowing that he had been drinking at the point they met him for a good 14 hours.