It appears from your symptoms, the polyps developed could have turned malignant.
Polyps are growth from the inner mucosal lining of colon. it is definitely a pre malignant. There are high probabilities for it. As you have also specified that she has severe constipation, probably the severe constipation could have hardened and pushed through the polyp causing it to bleed.
I suggest you check for her hemoglobin levels whether she has developed anemia due to blood loss. Go for a USG and consult a surgeon to take biopsy of the polyp, you would know if its turned malignant.
The treatment is to resect the polyp and treat your constipation firstly, use laxatives firstly.