Buyer issues

[thinkpinkandmore]

Long story short a buyer purchased an item on the 14th and contacted me today claiming they didnt recieve the item. Tracking shows it was delivered on the 18th. I provided the tracking and asked they go by the post office to see what info they can get. The response I got was that they discussed it and they want  another one sent. I don't want a negative comment but I feel like I shouldn't have to refund/or replace since per USPS it was delivered. Or should I just refund but then they could still leave a negative comment. I feel like Im in a no win situation here. What should I do? Thanks in advance for any and all input. Its really appreciated!