Can´t you have the code for the key and import it and talk to the girl. I thought of that after I posted my post.
Well i never saw the mage go down to Firkraag I only killed all the one and Tazok and the fellows but i saw no mage. He was with F. when I came to him. Then i talked myself out of F. went up killed the mage and then took the key. I OPENED the door before i talked to the girl. Maybe you should talk to the girl when the door still is locked?