I think may actually be the cold
I've just checked the symptoms of mild to moderate hypothermia and they fit everything that PR and some of the others have said. They're very like being drugged.
So shivering - which he's said.
Confusion - she was setting off in the wrong direction and getting lost, couldn't understand what was happening to her. Asking for her mum who was miles away.
Mumbling, slurred speech, poor communication - the darts players couldn't understand her.
Becoming combatative - telling people to f@#$ off.
Loss of coordination - falling over, staggering.
Plus becoming hypoglycemic as body uses up glucose supplies to try and keep warm.
It was minus 5 that night. She was dressed to go out. Bare legs, t shirt, leather jacket. Poor kid must have been perished
So I think everything that's been said so far is consistent with her bring hypothermic as well as drunk.