Are we talking about her rectal area (butt), or her vaginal/urinary area?
Rectal causes of bloody discharge are infected anal glands, gastrointestinal parasites, rectal neoplasia, rectal prolapse, and others.
Causes for bloody discharge from the vaginal area include urinary or kidney infections, vaginal infections, uterine infections (pyometra) if she is not spayed or inadequately spayed and more.
She should be checked out by a vet ASAP. Bring a fresh urine sample fecal sample in separate containers if possible.
Has she been spayed? If she hasn't, this could be a life-threatening pyometra.
Please get her to the vet asap as the symptoms you are describing are potentially very serious.