Step 1 – Ask her to ask for the refund through paypal not ebay. This is important.
Step 2- You explain to paypal that it was working when you sent it, and is now not working. Appears that it was damaged in delivery by the ebay Global Shipping Programme
Step 3 – paypal will refund the buyer, you keep your money from the sale, and ebay GSP will pick up the cost. They are liable for delivering the item in working condition.
This approach gets it resolved in around 24 hours.
If she asks for the refund through ebay this approach will not work, it must be through paypal.
I have had this happen to me twice, and got it resolved both times. I have now stopped using ebay GSP as I find they damage items.