Can you diagnose this?? We are baffled! Please Help. What could it be ---->?

No one can diagnose your sister over the internet, however they can encourage you and point you in a positive direction. She needs to see her primary physician who will do a complete physical. The testing she receives should depend upon the physician's clinical findings, but ruling out Hashimoto's thyroidiitis, Grave's Disease, PDD (Premenstrual Dysphoric Disorder), or one of the Bipolar Disorder variants would be starting points. Her physician will also do a neurologic exam. They will need to rule out any type of space occupying lesion in her brain. Very best wishes.