I tried something a bit different before reading this, I think your idea is a good one. I actually fed her later at 9 instead of filling it up hours earlier, but announced my presence. She seemed to like it, gave me some happy chirps and we talked a bit. No luck in getting her out, but maybe if I keep it up she will come out just a bit earlier. If it works, I'll try slowly moving it earlier.
Cupcake had dragged the puzzle ball into her castle, and solved it. She dug a little hole right to the center. I put a seed each in her willow balls, and will refill the homemade one.
Puzzle Ball Solved