in which I am proud of my cat

That went well, and I mean that in the literal rather than the Firefly sense of "went well".

Lily seems not to be actively scared of Sonja. She's cautious, but curious, and she never took a swipe at anybody. I ended up engaging in a bit of diplomacy of the "look, I'm not going to let anybody hurt anybody, so you (Lily) can come out from under there, and you (Sonja) can stop being attached to my leg, and nothing awful is going to happen to either of you" sort with Sonja in the hallway and Lily in the bedroom and a gate in the middle. Lily is the one who knocked the gate over eventually to come find out what the heck was going on, and after something like three hours I had them both sprawled out on the living room rug getting their stomachs scratched.

Dogs and cats living together! Hooray!