If she is just days old, it is probably from a peck to her eye. Look into it for any dirt or bedding, gently open the eye and put some saline eye drops in to wash it out. If it starts draining or she keeps it closed, get some Terramycin Eye Drops or Vetericyn Eye Gel from your feed store.Those are pricey, and I have used plain Neosporin in my chicken's eye without a problem, but those 2 products are specifically for eyes.