Obviously her body is not functioning well in relation to what she's taking in. I've found in my holistic practice, that there's many factors, some fairly well known and some very obscure but critical.
I have had constipation issues throughout my life and whole grains, specifically whole wheat, give me problems in this area. Since I've been paying attention to foods that are in my blood type diet along with foods that are 'cooling' and 'sweet', it's not an issue. Often, the suggestions of what makes sense, is often detrimental. We are all so unique!
I know this may sound weird but if you would be open to sharing her birth time, date and place (privately of course), I can look in her design (from the Human Design System) and see if there's anything that might jump out. Also, if you know her blood type, you can begin there as well.
Medicines are beneficial to assist at times but I would suggest that there's something off on a foundational level for her. For her best health now and ongoing, it would be beneficial to see if you can root out the factors.
If your curious...more info is available at TheMythAndMysteryOfYou.com
Best to you!