I'm sorry but there is nothing more insulting to me as a designer with over thirty years in the business, than having a total stranger with no background in design, second guessing my years of knowledge and experience. Especially when their background is in another industry.
I'm working on an expensive carved sign for a client right now, who after I explained quite clearly, why what they wanted violated very known design principles, and after their weekend family discussion, insisted I do it wrong as they requested. So, I will accommodate their request, which I do very rarely.
Pretty much everyone you deal with will have no background in design. They know this, but the more ballsy among them, who are also generally insecure about their ignorance, try to seem a little knowledgeable by pulling terms out of their rears. Some of these people even think it's helpful. Your response is usually the right one; try to educate the client about proper design and layout. That's not what took place in this instance though, and I'm not sure it should even apply.
He did well with little information. She did not "second guess" him, just tried to steer the design in a direction more akin to her interests. She didn't have the language available to be able to communicate her ideas fully, and admitted so. It's our job to deal with those types of people, give them a visual solution to a problem they are having, and take their money. That is not so difficult.
Edit: By the way, I definitely do not adhere to the "customer is always right" mentality, and the above has nothing to do with it. It's our job to provide the best solution possible, and educate the client on why it works, not just give them what they want because we can't be bothered.