Maybe Von Pinn is the "Other"? Think about it Von Pinn could travel from into the past using the "time windows" and decide that the best way to protect the "female Heterodyne" would be to capture her and give her to the Geisterdamen to watch over. As some people have theorized that durng the flashback sequence the Geisterdamen were giving. There is an arm that looks a bit like Von Pinns. Now since Von Pinn looks a bit like Lucrezia she could have pretended to be her and gone to the castle and kidnapped Lucreazia and the female Heterodyne to satisfy her twisted view of keeping her safe.
Now I agree there are holes in the theory but I think we can add this to the list of possibilities. Even if Von Pinn isn't the "Other" she may have driven Lucrezia to become the other by doing said events.