This is hilarious because my female does the same thing every now and then. She will eat her joint supplements and not her kibble! One time when she did this, I attributed it to running out of her fish oil. But all the other times, I think she was just being stubborn or something. I feed my dogs at the same time every day (like most people). My rule is, if you don't eat within 20 minutes, your food gets lifted until the next meal. Trust me, they will eventually eat.
My problem is that sometimes she does this in the morning when I have to give her some pain meds, and I can't give it to her on an empty stomach. So if she does it in the morning, I end up hand feeding her at least half of her bowl and she decides to eat the rest or not.