Originally Posted by
leftyboarder
You cannot get airside in international terminal without a passport and a valid ticket / boarding pass. They can gain direct airside access of international terminal from domestic arrivals if their flight departs within 1 hour of your arrival, but since you've said there are 4 hours until her flight, they will have to take the landside walkway and go through passport control.
Yes, it is a separate onwards booking, so (with luggage) they would have to check in most likely. ("most likely" = unless they check in online and decide to travel only with hand luggage, then no landside check-in would have been necessary in theory)