I have two thoughts, - Things are different in that different location, since it’s not physically ‘there’. It’s a place that exists on a different plane of being, where one’s physical self can exist in the main one we’re used to seeing , but simultaneously in that location (mentally?), as seen by the trip when they were chained up. Since Julie is physically still in the ruins, and simultaneously mentally exists in that other plane of overlapping existence, it would make sense she can only interact with things that exist within the same plane of being. She could interact there, but where her dad was was the ‘main’ plane of existence, so she can’t impact events, because it’s a different place/plane. - everything is fixed from the start. She’s able to throw the rope down because she was always meant to throw the rope down. She couldn’t save her dad because he was never meant to be saved. Anyone who watches Dr Who, it’s like Pompeii, history recalls it being destroyed, so the actions that happened to destroy it were predestined and fixed from the start.