My Niece Is 32 Y.o. She Has Periods Of Muscle

My niece is 32 y.o. She has periods of muscle weakness in arms & legs, periods of confusion, hives with surrounding redness, fatigue. The doctors she has seen have r/o MS, ALS, Allergies & Fibromyalgia. The symptoms seem to occur 2 weeks before her period & last for several days after her period is over. Do you have any idea what she has or any tests she should have done? She has been to specialists but no one seems to have any idea what she has. She is going to make an appointment with a psychiatrist thinking maybe it is psychological.