Is there anything on her other side? I’m not convinced that the hen is dealing with fowl pox. It could be an injury or peck wounds. I would keep an eye on her to see if she is being pecked, and look for any additional scabs.
I had something similar on my pretty boy named Merci, I did multiple things, the one that dried it up and started seeing improvement from was Blue-cote. I used a small paint brush to dab it on the affected areas, for him, both his nostrils were closed with sores, if you zoom in on his beak you can see it