Low Dialostic BP. Treatment you advise.

My Mother-in-law was admitted into Hospital for Covid Positive and Accute Neumonia (18/25) treatment from 8th to 23rd April, 21. After Discharge, she is maintaining normal oxygen level, but still on medications. She is a patient of Diabetic and High BP too for last 25 years. For BP, she is having "Concor 5 AM" for last 2 years. For Sugar Control, she is being given insulin and medicines after discharge from hospital since she is continuing Steriods for lungs. Now the problem she is having of her BP fluctuations and Dialostic BP going down sometimes upto 47, specially at night for last 3 days. Her Systolic BP always remain in between 110 to 140. But Dialostic BP going down. Why this is happening and what treatment you advise.