I sold a vintage but never used three piece tea set for $50 including postage which cost me  $17.

It was made by my sister in ceramic class some years ago and I knew it to be unused.

The buyer messaged me after she received it and demanded a full refund because it had slight discolouration in the glaze inside. I would say it is merely an uneven application of glaze, and I must note that I did not notice it to be discoloured in all the years I owned it,

i of course gave her a full refund, as sellers have few rights these days and I knew the buyer would win any dispute.

She didn't want to return it at her cost.

When I gave her a refund through PayPal, I asked that seeing it was not to her liking could she donate it to a charity. After all, she had obtained it for nothing.

So I am surprised to see that she has listed it herself, 

is there anything I can do? We are at the mercy of these of people, who probably make a little business out of this practice.