Through Zan's contribution, Peridot doesn't stop scowling critically at Penemue. It's not that she couldn't hazard an educated guess at what what the architects reasons for inaction were; she's just of the opinion that they're bad reasons, considering the Furies were actually out there trying to do something about Lilith.

Either way, she keeps her mouth shut for now, and looks up at the reflection as directed. It takes her a moment to wrap her head around the trick, but she joins everyone upstairs a few moments later.