Hi there and thank you for your question!
The causes of premature graying of hair are unclear. Some research suggest it may be associated with a medical condition, nutritional deficiency or genes.1, 2 I encourage your daughter to see her doctor or a qualified healthcare professional to assess what the underlying issue may be.
I hope this helps you!
In good health,
1. Kumar, Anagha Bangalore et al. “Premature Graying of Hair: Review with Updates.” International journal of trichology vol. 10,5 (2018): 198-203. doi:10.4103/ijt.ijt_47_18
2. Robert H. Shmerling, M. (2020, June 23). Why does hair turn gray? Retrieved July 31, 2020, from https://www.health.harvard.edu/blog/hair-turn-gray-2017091812226