The night seemed to go well (for the cats anyway, the people didn't do a whole lot of sleeping). Kitties had their first encounter this morning through the gate. Thought it was going okay, but Simba hissed and yowled. But most of her hair still laid flat and her ears didn't go back all the way so it could have gone much worse. It took Anubis a minute or so to hiss back. Simba took off for the bedroom, he retreated and James had to calm him down but everyone seemed to be okay within a few minutes (except me who is a nervous wreck - you can know all the steps and processes but when it's your own and emotions get involved it makes things rough).
Simba came back to the living room after a bit and ate a little, started to play with her toys so all is well again. We're not going to push the issue. They know there's another cat there, now we just have to let them do their thing and hopefully both will get nosy enough to meet again and maybe it'll go better next time.
I tried to feed Simba some treats in view of the gate. She started to pick them up and shake them but wouldn't actually eat them. She kept looking back toward the gate like something was going to come take her treats from her. But it's a start. And she's not used to me feeding her anyplace but beside her bowl anyhow. So I moved them back to her food bowl, she crunched them down and seemed fine.
She got back to playing again, and I noticed some little food bits around the bag of Anubis' food. Looks like somebody's been nosing in. No wonder her food bowl is still full this morning. She skipped right past her diet food for the good stuff.
Later in the day she actually played in front of the gate, and the two cats eyeballed each other - no hissing this time. I think Simba's primary issue is making sure she isn't going to be replaced. She is displaying some mild signs of separation anxiety - I tried to close the bedroom door to change and she started to cry loudly on the other end, so right now all doors must be open where I am.
All in all, it's been going much better much earlier than we expected. It looks like we may be able to take the gate down by next weekend, since they don't seem to be aggressive toward each other so much as wary and avoidant.
Wish us luck.