If she was discharged and cannot serve why is she reporting for duty ?
She has time on her enlistement contract. She had to serve so many years on active duty and upon release from active duty if one still has contractual time on the enlistment, they can go into a reserve unit that does the weekend drills or the IRR. In either case they are subject to recall. It is of interest to note, that while this does not happen often, those who are retired from the service may also be subject to recall.