I think you should do the right thing. You posted it, you made an agreement and backing out of that would not be right. You no longer wanted it therefore the value is not truly there in it. And I doubt anyone would pay that. If you chose not to do this I would then make sure you let her know you have had second thoughts and are so incredibly sorry. If your selling on Ebay your rating might take a huge ding. You could lie and say something got spilled on it its ruined but you have to look at yourself in the mirror. I would go with plan A. You wanted to sell it, half off is still more money than you woke up with and its a clean mind you have when done.