Well, we don't know anything about her, i.e. age, weight height medical history. And to be honest none of us here are doctors, so there is little point in you giving the information 2nd hand. She may not even be entirely open with you.
If I were her I would go see a doctor and tell him the truth, especially is she has some medical history.
Or ask her to come on this forum herself and ask questions, which is really what she should have done before starting a fast.
I don't know what she is fasting either, do you know why?