Ariana says the deal with the orcs to not invade the nomads if she stayed in the caves as their prisoner was a lie. They are about to attack the nomad camp.
She asks you to kill Advisor Kre'lak ( -63, -39, -55 ) Copy/waypoint -63, -39, -55 to slow them down. He is the orc you kill to get access to the lower levels of the Wailing Caves.
You then have to warn her husband Orwen Neovra in the nomad camp ( 394, -47, -809 ) Copy/waypoint 394, -47, -809, in the The Commonlands.