Hello Sir
I can certainly understand your concern.
I have worked through your attached query in detail
As per your narration, the possibility of orthostatic hypotension ( low blood pressure which changes with body posture) should be strongly considered.
She need to consult a qualified General physician or Cardiologist.
Next Steps
ECG
Thyroid profile
Complete blood counts
Serum
Electrolytes
Above tests have to be taken
Health Tips
Maintain adequate hydration by taking 2 to 3 liters per day.
Increase your salt intake
Elevation of foot end of the bed