Well, I did what needed to be done.
Verdict is: multiple breaks in the femur right below the hip joint. The muscle was lacerated as well, though I suspect that happened during the death flail.
Then I put her in the stew pot, marinated by my tears. Not a lot of meat on her; she was mostly fluff.
Learned my lesson; that won't be happening again. It's extra sad I had to lose a hen to learn that, but it'll protect the rest of my flock for sure.
I do actually have someone who could use her meat. I have a rule against eating my own pets and she was kinda half pet, half farm beast, you...
Long story short, I went outside Friday to discover my goats had knocked a pallet over onto one of my alpha hens and the vet confirmed today what I had figured out but with more detail:
Her right leg is either dislocated and fractured at the hip or her femur is broken and the grinding feeling...