We know Cersei used a lot of the hidden caches of wildfire to blow up the Great Sept of Baelor in the season six finale, but surely she kept some wildfire at bay for a rainy day?

According to Jaime, there was wildfire hidden practically everywhere in King's Landing, including beneath the Red Keep itself. We're not sure why the explosion at the sept didn't start a chain reaction.  

If the wildfire is gone, she probably has the Alchemists' Guild at her fingertips to prep some more if needed.