I have seen this a lot in lab and pet-store mice. The first thing to do is see if she has enough toys and things to play with and explore--toilet paper tubes, an exercise wheel, something to climb on. If she does, and is still tail-chasing to the point where it interferes with her necessary behaviors (eating, drinking) she may need to be euthanized to keep her from starving or dehydrating to death. I would watch to make sure she is still eating and drinking enough to sustain her activity level, and consider euthanizing her if she starts losing a lot of weight.
In short, provide toys and a wheel first, and if the behavior persists or gets worse, watch for signs of starvation/dehydration. Best of luck.