I don't think it is broken. I let her out today for a while and watched her walk. Other than favoring it a little bit, she uses it normally, but I don't know of any way to tell for sure without an x-ray. She lets me manipulate it now without complaining, so I think it is starting to feel better.
It truly was an accident on the horse's part. It was my fault if anyone's. I didn't see red girl in the stall and let one of the mare's in for dinner. The barn is darker than outside, and I don't think the mare saw her either. Then there was a screaming chicken and a startled horse. The mare is very kind, but she is a draft cross, and not very agile. Thankfully she is barefoot.