Bleeding from colon with hemoglobin at 6.3?

My daughter has a friend who's mother was diagnosed with hepatitis c many years ago (she was a nurse). She is in the hospital now and we have been told that she is bleeding from the colon. She was given a blood transfusion but "it just came right back out" and that her hemoglobin is at 6.3. How dangerous is this and why would the transfusion "come right back out"?