I know with dogs, and occasionally with cats, butt-scooting usually means issues with anal glands. If you don't know what those are, they're 2 little sacs on either side of the rectum. They fill with a gross fluid which usually empties when the animal poops. However, sometimes the animal is unable to release the fluid on their own and they need a little 'help'. It's not pretty, and should only be done by a vet or someone trained to do it. If not taken care of anal glands can become inpacted requiring medical attention and occasionally surgery to take care of it. So if you've tried all the other roads and there's no dingleberries, or worms, go to a vet and have her anal glands checked out.