Do her eyes look red? If so, she might have pink eye and should see the doctor -- it's very, very contagious.Sometimes it comes on at the end of a cold, so that could be it.
If she does have pink eye (or until you're sure that she doesn't), wash your hands constantly and don't touch your eyes if you can help it. I know this firsthand as pink eye ran rampant through my house last month!
Good luck, hope she feels better.