A normal blood pressure reading for a 75 year old woman or anybody else should be around 120/80 and if it gets lower than that then the person needs to see a doctor or seek medical attention.
If the blood pressure climbs above 120/80 then the blood pressure is starting to get high and the person is going into prehypertension.
Try taking a walk of around 15 minutes to lower your blood pressure if it starts to rise and take a tablespoon of apple cider vinegar which too can lower your blood pressure.
If your blood pressure stays high then you need to see a doctor about it because high blood pressure can cause serious medical problems such as stroke, heart disease, heart attacks and damage the blood vessels.