Buyer provided a wrong address and she wanted a refund. What should I do?

[happi*mandy]

Buyer bought an item from me about three weeks ago and recently we found out the address she registered on eBay is a wrong address (which is her old work place). 

However, the item has been sent to her eBay registered address which is her old work place by normal standard post. Buyer said she rang up to her work place and there is no parcel arrived yet.

And now of course she is asking for a refund. So what should I do? Advice some other sellers is much appreciated.

p.s. Buyer paid the item by bank deposit.