My 56yr Old Daughter Has Had Constipation. Problems For About

My 56yr old daughter has had constipation. Problems for about a month. Her dr. said it was from some meds she is prescribed. She will not have a bowel movement sometimes for a week. During the week she takes stool softener, large glass prune juice, bran cereals , fruits etc. She still doesn’t go for all that week. What can be her problem?