I would suggest an ENT evaluation. Singers are prone to vocal fold pathologies. She would want to rule out vocal fold nodules or other problems. She would need a doctor referral to a speech pathologist who provides voice therapy, which offers treatment. There are some articles on good vocal hygiene to try in the meantime.
Has she been ill? I'm assuming she knows how to properly warm up the vocal cords. I would absolutely consult with a physician on this and do so sooner rather than later. Let us know what they say!