There's not a whole lot to support this, but they're seen conversing, quite civilly (all things considered) and obviously not for the first time.
It makes Michael being the one to pour the holy water used to execute "Crowley" dramatically appropriate, as well. She's probably eager to kill the guy who murdered her friend, but has to keep it under wraps.
This is based on Crowley's hypothesis that God's "ineffable" plan is for the real final battle to be between Humanity and it's supporters and the combined forces of Heaven and Hell. Assuming this is the case, then logically those events would wind up being covered by the show.
All the other children have backstories but Brian isnt given one. His name could be a nod to Life of Brian, where he is the messiah.
- It isn't a nod to that. The name is from the book, which eventually reveals that the other baby at the hospital was adopted into Tadfield, and he's the leader of The Them's rival gang, the Johnsonites.
- Or it shares a community with World Of Darkness, where the Almighty is also a woman, who holds both angels and demons for fools and has her own plan.
Getting bored as time goes on, or deciding to do more good, Crowley assumes the name "the Doctor", and starts taking people to more places and worlds. Maybe he also uses the place Galilee as inspiration for the name of his "home planet", Gallifrey.