Fanny was trying to get through the barrier, so I released her into the general population, figuring her stress at being confined was as much a problem as anything at this point. She is doing better but still precarious and totally covered in fungus (though she seems to be shedding some). I will be picking up the aquarium tomorrow, so hopefully she'll be fine.
An interesting point that I find worth mentioning. The koi seem to be protecting her. As had been the case while the spawning was happening, I had to rescue her from the skimmer this morning, but one of the koi was planted in front of it until I took her out. (I left her in there for a while to give her solitude, but then she seemed to be spending too much energy to resist the flow into the pump. The filter pad provides a 100% barrier to the pump, but it is dense, for mechanical filtration purposes, so I thought it best to let her out despite my conerns about spawning. The guardian koi was by the skimmer the entire time Fanny was in, but not since.) After I released her, that koi has never been far from Fanny. And when the guilty adult shubunkins and comets drift close, both that koi and a second one (the largest fish in the pond) literally run interference. I watched this behavior both when I first released her last night and for at least an hour today, so I don't think it's a coincidence. Has anyone ever heard of fish doing this? The orfe have been solicitous of her health as well but not acting as guardians like the koi.
Thanks again for everyone's expressions of concern. I'd put her odds now at 60-40 to survive: better than yesterday, but still far from being out of the woods.