When a customer makes a very specific request, it's best just to honor it. You never know what they're going through, or how dire the consequences of not following through could be. Yes, okay, a LOT of people order gluten-free just because it's trendy and not because of actual celiac disease - but all it takes is ONE customer who really does for you to end up on your a** or in court because you thought you knew better than them. Take customer requests seriously, because ignoring them can have serious - sometimes even fatal - consequences.