Hi there, that's not from a fall because a piece of it is missing. That would be from getting caught under something very heavy [ or in the top of an enclosure ] or being bitten . Do you have another dragon with her ?
Post pics of it when it's dry and BTW, soaking it is more damaging because the water would have bacteria [ from her body, dirty feet, etc ] that can enter the wound . The only way that soaking could be helpful is if you put about 10 parts betadine [ enough to make it look like iced tea ] but don't let her drink it. Some people just put the water/betadine in a jar or something and let the tail dangle in it without the entire body getting soaked. You can also use neosporin on it or raw honey. Make sure there are no loose insects in the tank to bite at the tail.