Well, she called again and one of my decorators explained that, because she did not bring in the cake the same or next day after the party it was difficult to refund the cake site unseen/tasted. She threatened to withdraw the funds thru her Credit Card company and said for the owner to call her.
So a few hours later when I had decided what to do, I called and played dum, as if I didn't know what was going on. She explained that the cake tasted weird, as if something was left out. I realized that the cake had turned so I asked her when they ate the cake. She said that although they picked up the cake Friday morning, she didn't serve the cake until Saturday around noon. I asked her if she refrigerated the cake and she said no . I asked her the temp in the space the cake was kept and she didn't know. I explained very sweetly as per all of your recommendations. That I had a cake from the exact same batch that had been in the fridge since the cake was baked on Thursday and it still tasted great on Monday. I went on to explain that we have no control over our cakes after they leave the shop and that a cool place for cakes is around 68 degrees or refrigerated. I told her that I was sorry, but that I know the cake was perfect in everyway when it left the shop, that the cake has dairy products in it and that we open our doors at 8 AM specifically so that our customers will eat their cakes the day they are prepared. I finally also said that based on her experience we would be willing to give her $10.00 off her next cake purchase. She said that she had been recommended by a member of her very large church and that she would be sharing her bad experience with everyone and then she hung up. I'm thinking somehow in this 110 degree heat and humidity in Texas it wasn't stored properly but I did judge her pretty harshly must not be getting enough sleep. Thanks everyone for the support.

I am pretty sure your cake was wonderful and this lady had buyer's remorse. However, did you inform her when she picked up the cake on how to store the cake and that it needed refrigeration? Also, do you have this on your contract/invoice?

glad its over with, sounds like you handled it as well as you could have, without being too harsh.
You think common sense would take over, let's see- cake left out for that long in warm temps.... hmmm... especially with such an important event.
Jodi