angry customer... confused, please help!

I'm a baker and I make custom desserts. I had a pretty detailed cake order from this weekend. The customer was pretty particular about what she wanted, which is fine.. I appreciate clear direction. But I could kind of tell that she might be a difficult customer. I delivered her cake yesterday, and she was thrilled. She said it was just what she wanted, and that it was beautiful. Fast forward 2 hours, and I get an angry email from the same customer saying that the flavor was all wrong, that the cake was too sweet, etc. I taste test every single order I make to ensure quality. I also use real butter and sugar, none of the fake stuff. So if you're used to a grocery store cake, my cake is much more rich. I'm good at admitting if I'm wrong, and offering compensation for an unhappy customer... but in this case, the cake was pristine, I know it tasted great, the flavor was correct and I have sent her proof of that, but yet she's still asking for 100% refund. Should I....