Well, I just spent about 40 minutes trying to catch her, and it's not going to happen. I pulled out all the cabomba and the asian ambulia to make things more open, fed the fish, and used two nets. No luck. No problem catching any of the other fish though - they were all eager to ride in the net - go figure
Having worked in an LFS in the past, and had considerable experience netting fish, I can say that she'd be near impossible to catch. She's the worst kind of fish to catch: small, shy, doesn't panic, and uses cover to her advantage.
Lowering the water level would work, if it wasn't a densely
planted tank, that also has lots of hardscape. I'm simply not willing to rip the tank apart to catch one little fish.
The fish trap would work, except that she's not the only fish that size in the tank. I think I'd be more likely to catch my yoyo loaches, SAE, or glowlight tetras in the trap than the nannacara - nannacara are really shy, smart little cichlids, and very cautious of anything new in the tank.
I'll just have to let things take their course. She'll either get better, or die. I suspect the latter, as she's suddenly started courting my male, who's been chasing her without response for weeks, but she's not in spawning colors, and looks, well, awful. I figure the spawning behaviour is a last-ditch effort to reproduce before she dies. She's still active and eating though, so who knows...