Bipolar and Fasting. Advice?

My sister-in-law is inspired by my fasting (10 days today, yay!!) and would like to try it as well. However, she has a diagnosis of Bipolar. She has been treating it primarily via counseling, exercise and behavioral modification techniques. Anyway, does anyone know how fasting might work for someone in her situation? Will she swing into a mania? I obviously wouldn't want to be responsible for having her do something which will jeopardize her mental health. .... Any thoughts on this greatly appreciated!