Well...I failed, although at least I tried. She started getting really weak again late last night and then, earlier today, another bunch of muscle and other tissue suddenly fell off from around the damaged area, exposing the spinal column. That was what I was hoping to avoid since I knew she'd be toast if it got to that point, but I guess there was no stopping it. She lasted a little less than an hour after that happened. I don't think continuing the formalin would have avoided this result, since I still don't see any evidence of infection. Of course, I'm not equipped to detect something like a virus if there was anything cryptic like that involved, but it seems rather unlikely and the formalin wouldn't have helped then either. More likely some organ or another was hit hard from ingesting toxins and it just didn't give out right away.
On the bright side, everything is going still going strangely right in the 55gal. Peppermints are very aggressively getting rid of the Aip problem that has been lingering on one part of the rocks, and some green Zoas are going crazy making new polyps for me.