Not a metaphor. Not the slightest bit a metaphor, and frankly it's more than a little alarming that she's just living in someone's flat if she's really carrying about a strain of mind-controlling fungus capable of overwriting human beings. She's right, she mustn't go back to ROMAC, but here isn't safe, either. The TARDIS -- he'll call up the TARDIS and ask her for help, because if anyone can safely house a highly infectious little girl --

Andrew doesn't hear a thing before a hand appears on his shoulder, and he gives a visible start. "Ah," he says, allowing himself to be turned. He offers the other man the most innocent of smiles. "I take it you're Aziraphale?"