Is there any lesion that was noted in the middle of the tail sometime in the recent past or was she at ever recently sensitive in the middle of her tail? The reason I ask is if there is any nerve damage there, then she will not know that the tail is in fact hanging down. The danger of this is that if she cannot feel the end of her tail, she is at great risk of traumatizing it without her knowledge and this can lead to sepsis or fatal bleeding etc.
One of the ways to test is to really pinch the tip of her tail with your fingernails until she feels it and reacts…if she doesn’t then you need to have her examined. Sometimes it is necessary to amputate the non feeling portion of her tail to avoid injury.
On the other hand there may just be a behaviour aspect to it. If she is clinically eating and drinking and acting herself then there is likely no need to hurry in as an emergency, but rather have it checked out to be sure.
Martin Slome DVM
Centre Street Animal Hospital
7700 Bathurst Street Units 40-42
Tel. (905) 771-9855