Mesh,
It seems that JSL's company DO say which side to go. And her point is that on some types the cabin crew are not in a position to make that judgement.
And how many times have pilots called for an evacuation with other information, leaving the cabin in no position to make a judgement.
I was running a CRM class recently and one CA was telling me of an experience she had. Pax had not boarded so empty aircraft when suddenly the captain called 'evacuate'. She put her head through the door and asked what was going on and all he did was shout at her to get off the aircraft. So she left. But there was no sign of the pilots following her. So she reboarded ... only for the Captain to start shouting at her. She was concerned that maybe they were incapacitated. 20 minutes later the pilots emerged. They'd had a smoke detector go off in the cargo compartment and had decided to stay on board to guide the fire trucks to the aircraft.
I mean, what's a girl to do!?