Rose can fill in the same blank, honestly. While she hadn't lost anyone to the demons then, she remembers how ugly. How bloody and awful their infestation was. Her own kind liked to tear the flesh from people's bones and she has too so she understands just how horrible demons can be. Whether they be the kind that plagued Hadriel or her own kind. She knows his fear isn't founded in something irrational.

"It's not fine, but. I get it. We all got shit that we're afraid of, even if it might be... Well, not unfounded. I mean, we usually fear the worst things that have already happened to us repeating so. Your fear is demons. Mine? Water." That might seem anticlimatic, so she clarifies: "Well, drowning. But I mentally flip out if I get too close to a body of water I can possibly drown in. So I'm not having a good time with these pools and I know it's not exactly the same, but."