But hey, that moment between them at the end of their scene is easily as much setup as Buffy/Satsu had, so I'm hopeful... ;-)

I'm afraid Faith getting with Buffy (or Giles) would fanservice me. And the season is determined not to do that :(.

was it really such a good idea to teleport away in front of everyone? Wouldn't it have made more sense to have them continue to think they're doing well (however the hell they could possibly think that)?

I'm not absolutely sure. I thought Andrew wasn't through. He's pompous, but to call them all in should he not make more of an announcement then "it's not willow?" It could be that the cat made her exit so obviously so that no one would search for the real traitor anymore. Maybe whoever is it just made a completely normal cat dissapear. That would be kind of cool.
So it's probably not the case...