Generally any type of anti cribbing spray or rub that has cayenne pepper in it should do the trick. You can get them at most tack stores, or you can make them at home. I'm pretty sure you can just google cayenne pepper rub to stop chewing, and recipes will come up. I just don't have any off the top of my head. Make sure that the tail is coated in the stuff when you put her back, and make sure to wash your hands after using the stuff, as it does burn if you get it in your eyes, or around your nose, not to mention it tastes nasty, which is why you would use it. I have heard of some horses before actually liking the Cayenne, so you need to maybe take pictures, so you have something to compare to, and make sure that the chewing isn't still going on. I've also heard that a lot of horses don't like the taste of MTG, so you may want to try that as well, and the added bonus of MTG is that it helps the tail grow back as well. Good luck, I'm still dealing with my horse's tail having been chewed, and its annoying as heck.