Has she somehow cut her tail? This is a hard place to get the bleeding to stop because the dog is always wagging the tail. You will need to put a compression type of bandage on it until you can get the dog to the vet. Do NOT wrap it too tight though as it can cause more damage. Your best bet is to wrap it thick with cotton and then some medical tape all around the cotton and up the tail a little ways on the hair so it will stick.
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