My GF have constipation problem too. Tried many method which has been recommended. However for long term, things doesn't seem to work out on my GF. This happened since she is young.
But for normal constipation, it helps alot. (Like for me)

1.) Organic Prune Juice (Lakewoods brand is good compare to other brand)
2.) Biogreen Organic Green Balance

This 2 natural food, i feel it is most effective as compared to other supplement/food. Feel free to try them