You need to move up the vet visit for your dog in order to avoid any serious permanent injuries to her tail muscles because it may become too late to operate. Meanwhile wash the wound thoroughly with soap and warm water to avoid infection. Apply an antibiotic ointment such as Neosporin on the area and then place sterile gauze pads over the wound. Ensure that the dog does not go into an area that will expose her to more injury.
'a few days"??? Why so long of a wait? Broken bones usually take priority, because if they have to operate to save her tail, they will want to save as much as they can ... the longer the wait, the worse it is. I can't imagine the pain she is having to endure.