The reason the FA could have looked as if she was about to faint was probably becauseshe had just operated LGW - KIN 91/2 hours and entitled to no rest, about 1 1/4 hours on the ground in KIN and then onto MBJ. Only the flight crew get off in KIN, the cabin crew stay with the aircraft, and if the flight is on a Thursday, they get a layover of about 18 hours before flying MBJ-KIN-LGW!
That is probably the reason she was dropping of her feet!!!
Regards