Thanks for the advice everyone. My wife just called from the gas station. She was going to put the 110 octane in the tank, but the nozzle was too big. Instead, she topped off with non-ethanol premium.
It just occurred to me that if the check engine light comes back on, I can siphon the gas and put it in my van. Then I can fill her tank completely with premium fuel. Luckily, the car is under warranty. So, if it turns out it was a just a coincidence that the check engine light came on with regular unleaded fuel, we shouldn't have to pay for a repair.