I am sorry about your little one! As a Vet that DOES see chickens, I am sorry to hear you were unable to get the help you needed when you needed it. I have treated many chickens mauled by dogs and I can tell you Chickens are the toughest creatures in the animal kingdom (in my humble opinion). From the picture you posted it looks like there is evidence of healing by third intention (from the outside of the wound in). This is a good sign! I would anticipate if your chick has made it this far she has a good chance of making a full recovery. Keep her in a warm, draft free area and try to keep her booder as free from fecal material as possible. If you are using shredded paper or sawdust bedding- get rid of it and replace if with paper towels or a puppy pad or even an old bath towel if you don't object to washing it when it gets covered with poop. Discontinue the aspirin- it can damage her liver and kidneys (and please don't ever give it to your dog). I also recommend not using hydrogen peroxide in the future- our mother's lied to us, it is terrible for fresh wounds- it kills tissue and all the wonderful body helpers that invade fresh wounds to promote healing. Next time opt for dilute bedadine (iodine without alcohol).
I would continue to clean her wound daily until the wound is closed or covered with a solid scab. After that, cleaning won't be very beneficial but application of Bacitracin or Neosporin every 12 hours will help keep the scab pliable and prevent it from cracking. I have had infection develop after a wound has closed- watch the tautness of the scab, if material is building up under it, the scab will appear tight and shiny and may pull at the edges of the wound. As far as her tail- time will tell. Her uropygial or preening gland is located at the base of her tail- if this structure has been damaged she may potentially have trouble grooming. I took a Rhode Island Red hen to surgery after 'something' (prob. a fox or raccoon) essentially severed her tail. Two hours of surgery later she made a full recovery and has a very functional preening gland, so I would anticipate your girl should be just fine- Nice Job! I can comment further if you are able to post updated photos.