Also make sure's she had thryroid test within that past year as both thyroid and celiac are common autoimmine diseases with type 1 and constipation is a sypotom of thyroid disease.
She may have to have some help beyond diet changes. That's a long time to not have a bowel movement. I am not speaking as a doctor, but as a mom. If this is a one-time event, she may still need to be seen by her doctor in order to have some help. After that, though, I would suggest that you look very critically at her diet. Is she getting lots of water? Is she eating a high-fiber diet? Lots of fruit and veggies? Maybe it is time to reevaluate and remove foods with white flour to make room for the healthier foods. If she has digestive problems often or complains of pain, I would ask her doctor to test for celiac disease, for it is farily common among type 1 diabetics.