I think that when a business person needs the order, that gut feeling goes out the window. If anyone can learn this lesson from us seasoned business people, you must learn to turn away these people. Your competitors already did.
For example, when working with a customer, I refer to the price up front, my payment policy, etc. No one ever asks me to let them pay later or disregard core policies. They see that I have all stages clearly in order, so those bad customer manipulations would be too much trouble to try on me. That refund policy, addressed at the time of invoice, shows that the refund excuses I see sometimes on CC just won't work with me. But it also provides the customer insurance that if I do make a mistake, they are protected too.
If you do decide to deal with the customer, be proactive and cover your bases in writing, even down to the ingredient changes. In this situation, when you know the cake is perfect (I'm referring to my specific refund policy), you can confidently call their bluff, and that firm business stance (which I get blasted for on here all the time) will cause them to see that after the sale, you will not put up with them. They will go away and forget about you. But if you stay meek, or too accomodating, or nice, or empathetic, they will badger you. I'm not saying be rude, but have a protocol in place, feel good about it, and stand behind it.
This family sounds like a bunch of scammers...I have met people like this and it is their way of life with everything! Order a product or service and complain in any way possible to try to get free stuff or money back. They do it with big ticket items and services, like airline flights, and they do it with smaller things like cakes.
Any family that comes in your shop 3 times in a few days is most likely to be high maintenence and a problem customer who will never be happy. I can't believe the aunt actually called you a thief! Even IF the cake wasn't "authentic enough" for them, what kind of people harrass the baker? Normal people would just chalk it up to a lesson learned, maybe next time get a cake tasting beforehand if they are so darn particular! But these people just aren't normal..and I bet you anything if you trolled/ investigated these people's facebook pages there would be pictures of their celebration with a fully eaten cake!!! The nerve of some people!
Oh no I was not referring to Vaniti716's post I truly feel for her. It was tho other one complaining about the grammar. Southerncross, not a problem I was shocked for your response, but figured I was not clear. I truly understand about the to much coffee, hey as a Retired Chief I know all about coffee! Anyway no hard feelings we are all a family in the cake decorating world.