Just another update on Dart's recovery, which is going spectacularly well, I'm happy to report! She's extremely energetic to the point where it's hard to get a clear pic of her, just like old days. :) Managed one capture yesterday:
Besides getting a bit of flesh on her tiny bones, her fins are getting longer and her color is just so much more vibrant. The rear tip of her dorsal fin is still kind of wonky, sort of bending over or collapsing, but it's steadily improving so it doesn't fall over anymore. I also noticed her right ventral fin seems to be kinked or folded, not sure what that means.
I've been feeding her crushed NLS Betta Formula food about twice a day (probably a total of two to three full pellets) with occasional bloodworm treats. Haven't bothered with any salt treatments or anything, just daily 25% water changes adding StressCoat. Oh and I increased her temperature to 79*, as CoolishPrune3 suggested.