So sorry about your hen. Can you hear any air escaping from her wound? Keeping her wound moist with saline, Vetericyn, Hibiclens chlorhexidene with water, or Betadine would be what I would do until you decide whether or not to put her down. Keep the wound covered with Triple Antibiotic Ointment so that it does not dry out. Is she awake and alert, can she stand, or is she able to drink water when you hold a small scoop up to her beak?
This wound looks very serious, and it might be best to put her down, even though that would be very upsetting to you. Doing the best for her, and not letting her suffer would be the best. If she can stand up and is alert, then use your judgement, and try treating her wounds.