Jonelle did something similar a few times not long after we adopted her. It happened in the family room and in the bedroom. It turns out she was watching the light from the TV bouncing off the glass coffee table, mirror, and anything with a reflection in it. She acted exactly like your girl in the video.
When she starts this behavior is the room totally dark? Watching the video, it seemed she was was noticing her shadow on the walls. I know at 4AM probably so, but some people sleep different hours, have the TV on, or sleep with a low light on. Just a thought.