You have to choose which countries to sell to in your setting when your are doing the listing , not only put it in your description or international buyers will still see the listing (and unfortunately a lot of people international or not, don't read all of the description
) . If I were buying internationally though I would not assume the shipping is free. Does your buyer think that she/he is actually getting free shipping? has she/he paid/contacted you since?
If I saw a listing like that, I would assume that the free shipping would only apply within the seller's own country. I would either cancel the transaction or ask her to pay the shipping
^^
I agree with Sebbys advice here - either you tactfully explain that unfortunately you do not ship internationally and cancel the transaction , or ask the buyer to pay for the international shipping.... although under normal circumstances ebay does not allow you to charge your sellers extra shipping, but this isn't a normal circumstance
Do you have a link to the auction? I'd like to see what you wrote/chose as your settings and desctiption. I'm in the UK so I'll see what your buyer saw