Of course she is not happy. if it was packaged well enough then it would not have broken. You could have asked the buyer to take it to the PO with the packaging to see if AP would take responsibility but obviously they are not going to do that now. I would have asked for a photo and then have refunded in full immediately without asking for it to be sent back.

If they open a Paypal dispute they will win and then you will have no option but to refund the rest of the payment anyway, you will be able to insist that they return it but as it has no value except as a 3D glass jigsaw.

If you are selling fragile items you should be adding a few cents into the price of all your items to cover the cost of an occasional claim.