If she is bleeding from her anus she may have hemorrhoids or she may have something called diverticulosis. If the bleeding is frank blood then she needs to be evaluated by a doctor as soon as possible. She also needs to see a doctor right away if she has dizziness. She needs to have a rectal exam, and abdominal exam as well, she may also need a CT scan of her abdomen

hi,
is there a swelling in the anal area, does she strain whe passing stool is she constipated these are the questions you need to ask her,
many causes of passing blood through anus, some that are from the anus region and there are those that are internal
the causes around the anal region include - hemorrhoids, anal fissure, anal sore, anal abscess which is burst, anal mass
the ones that are internal - colitis, ulcers on the intestines, diverticultis, ulcers of the stomach.
you need to take her to be seen by a specialist in order to know what is cause because otherwise she is lossing blood causing her to be anemic.
hope to have answered your query.
takecare and get well soon

Is she has bleeding is likely that she has either a fissure or even a severe case of hemorrhoids in case of an external damage, but with the bruising you mentioned there's also a possibility for the bleeding to be in the lower intestinal tract, either way I would recommend that she gets a proper physical examination by a professional so she can receive the proper treatment.