Why Does My Cat Bleed From Her Rear End?

Your cat probably has a intestinal problem and should be seen by a vet asap. Anything hing that disrupts the natural workings of the stomach and/or bowels can cause bleeding. Some of these problems are minor such as worms others are more severe such as stomach ulcers or cancer. That's why it's important to get it to a vet, any of those things can cause larger problems or even be fatal left un treated. Simply make your cat a vet appointment as soon as you can, it would probably be a good idea to see if the vet will need a stool sample for testing.