It appears from where I sit to be an abscess, probably from her other eye issues. Neosporin is the best thing to use on it.
There are other treatments, but chickens usually are not very cooperative patients. You can use hot compresses on it to draw out the infection or you can lance the pus. It would be a matter of putting pressure on the lesion to force the pus out since chicken pus is a solid, not fluid that will drain.
It's not necessary to do those things, though. It should heal eventually on its own with just the Neosporin.