Orthostatic hypotension. Kindly help.

My mother is operated case of squamous cell carcinoma of left lateral tongue and was operated on 2019 followed by session of chemotherapy and radiotherapy at Rajiv Gandhi Cancer hospital, Delhi. At present her follow up PET Scan report is cancer free. Since operation she is on semi solid diet.she is on herbal medication since 2019 with protein and vitamin supplement. She was fine till March,2022 , suddenly developed fluctuation in blood pressure.Morning 60/40 to 90/60 to evening 170/90 to 190/110. Leading to episode of fainting at morning and headache at evening.Her ECHO, Adrenal hormone,CT scan,ECG is normal.serum electrolyte sodium was deranged and was prescribed hyponat tablet for week. Still fluctuation did not stopped,was admitted to hospital twice ,once when blood pressure was 220/160 and second time when she fell in bathroom at morning due to low blood pressure.Only symptomatic treatment. It have been 5 months yet fluctuation in present.Presently on no medication.kindly help.