Where is here? I may have missed it - adding your location to your profile is helpful so we can give better suggestions.Update: This morning she is looking quite perky, eating, drinking, and having an annoyed peck at us when we were checking the wound. She has diarrhoea but I think that’s probably normal after stress plus maybe the aspirin? Her appearance gives me some hope she’ll live, though that gaping wound I am still a bit worried about. We have been using non-stick wound dressings from the first aid kit but this morning when checking it the wounds were starting to dry out and go a bit crusty. I haven’t been able to get any antibiotic cream/ointment (animal or human), we can’t get it here without a script but I thought I’d get some betadine cream today. About antibiotics though, I did see antibiotic powder for birds at the pet shop, which you mix into their water. Would this be any good?
If you are in the UK or Europe you likely have Germolene, that can be used on the wounds.
I would not apply a dressing to the wound unless she is picking at it, the wound needs to be kept relatively moist with your ointment(s) but it generally needs to breath in order to heal. Chicken wounds usually granulate from the inside out.
Here's some photos of what healing wounds might look like
https://www.backyardchickens.com/threads/wounds-pictures-of-how-they-heal.1325817/