When you don't know the ground -- when you don't know what's solid and what's quicksand -- you tread carefully.

Unless Gabriel's been doing a hell of a lot of theological study with Crowley in the free time he doesn't have, he doesn't know the ground any better than Regan does. Which is to say: not at all, not in any way that matters.

This is why her polite expression has just gotten rather more fixed, and her fingertips dig into Gabriel's arm.

If you're going to play checkers with the devil, she thinks at her husband as fiercely as she can, for the love of God don't TELL him that.