Request for Refund from Buyer

[neebpike]

Hi there 

I sold a china mug on ebay with no defects - the buyer has told me that it is damaged and that she thinks it was damaged before sending, due to the darkness of the crack.  I woud never have tried to sell it damaged.  I do question whether this is the same item.  She has sent me photos but I think this is a different mug - she is requesting a full refund. The damage photo (1) shows the label has been lifted and the advert photos (2/3) dont show any evidence of an 'old' crack,  as I say I would never have sold, let alone sent!!  I have zoomed into my advert photos (to check I didnt miss it and theres nothing)  I think this is a different mug - she is requesting a full refund.  Any ideas what I should do would be gratefully received?  Photos below

DamagedAdvert photoAdvert photo

[plpmr]

Adding to the advice already given -

the 'advert' photos are lighter than the 'damaged' photo and the 'damaged' photo is of the opposite side to the 'advert' photo.