Hypertension is something that can bring death on sooner but is more of a chronic disease. It does damage over time. What is your mother's blood pressure?
So, is it an anxious worry then if you aren't sure what her blood pressure is? I personally have high blood pressure. I take medication which lowered it almost immediately. But you have to know the numbers (and not from one reading) to know if it is hypertension or pre hypertension or normal. A blood pressure cuff at home, taking bp two or three times a day over a month or two really gives a pretty accurate picture. Maybe you could purchase one of those for her and ask her to track it?