Did it just appear? Could she have been stung by something and then scratched it too much?
Does it look infected?
I would probably try a warm compress. I keep Terramycin on hend for eye injuries. They may have it at your local farm store or you can get it from Amazon. If you don't have that I would apply a little vaseline just to hopefully soothe it.
It looks a little like a stye that people sometimes get.
I believe your pullet is dealing with fowl pox, a virus spread by mosquitoes. Most recover in a month or so. No treatment is needed unless scabs get around the eyes. Terramycin eye ointment or plain Neosporin triple antibiotic ointment can be put into the eye twice a day for prevention of a secondary eye infection.