Would it be possible for you to catch her and get some close-ups of her bill?
It's an actual condition, can happen. All hooves or Bills are like our own fingernails so definitely certain bacteria grow which causes a rot if in the right conditions.
Well, yeah, that's how rot generally works. Requiring bacteria or fungi to break down organic material. That's all athletes foot is. I can't actually find anything from a creditable source about "bill rot" however. Can you provide a link that is actually educational rather than a generalization of how rot works?
Call a vet. Best decision for all .
Ehh. You're probably right. The trained professionals would probably know best.
