I would not stitch it. What happens with any dirty wound when you suture it is that you sew the germs inside. It needs to heal from the inside out. I'd spray it with BluKote or put a little Neosporin or similar on it, after a gently cleaning. Be sure you avoid any wound cleanser or ointment that has a "caine" drug in it, such as cetacaine, benzocaine,etc., as these are toxic to chickens in small doses.
They usually heal up well with little attention. You may have to separate her for a few days to keep the others from pecking at the wound. If you have BluKote, hopefully the color will prevent pecking.