It's good that she uses the palace when left in it. The next step is to gradually expand her area. You can do this using an exercise pen or small room like a bath with the palace door left open. That gives her more room but keeps pad and tray in sight. After a couple weeks you can gradually give her more space.
Most puppies are ready for the second step with the pen after a couple weeks of being in palace whenever not actively engaged with you. As mentioned earlier moving the loft to the back when you add the pen can help.