As has already been mentioned, she should speak with her doctor. Sciatic pain is really a general term. It is important for the doctor to diagnose the cause of the pain.
We as fitness professionals tend to believe sciatic pain is a consequence of a pinched sciatic nerve, however there are other causes.
Too, for me, pain is an indication that an individual should see their doctor, if any of my clients say they have pain, I suggest that that see their doctor.
All the best to you.