Hinged window
From the context clues, a person can stand at a casement and wave with the possibility of people seeing her, and it not be strange. With that in mind, people don't usually stand and wave in a cabinet or trapdoor. That would be rather strange to see. The only two options left are door and window. It is most likely that the woman is standing AT the window waving her hand standing at the window. Usually you stand IN a doorway.
