Well it’s the customers fault and why oh why should you be out the product and the monies due to the customer not keeping her paypal information up to date.
Also even if she pays for another if she doesn’t change her details on paypal you will not be covered under paypals Seller protection.
Beware there is a con about where people order items then ask sellers to send to a different address than the one on their paypal account. Some sellers think ok I’ll do as the customers asks then of course the customer will say they never received the item and bring up a case in paypal. Paypal will then side with the customer as you the seller have not send the item to the paypal address so you lose the item and the monies. ie the ‘Customer’ gets your item and your monies. A
It is not your fault you are not to blame and I would recommend be firm, but polite and professional about refusing to send them another free item. If they are willing to buy another then get them to first change their paypal information.
Also agree that if the first order finds it’s way back to yourself in the same condition it was sent out then and only then will you refund.
But do not refund them until that happens and do not send them another item for free.