Sometimes when the alpha chicken gets injured/sick or even just a hard molt, it can change the pecking order within the flock. She can end up being on the bottom for a while. It sounds like this is what happened, but again, I would keep an eye on her for any other signs of illness. She has gone...
Sorry to hear about your chicken's accident. It's a good thing you copped it, sounds like it could have been fatal if that thing tightened!
As Wyorp Rock says, it does look like she's molting. I would also check her crop first thing in morning and keep an eye on her for a few days. Chickens...