The relationship between stress and high blood pressure
has to do with the interaction between stress and the release of certain hormones. During times of stress, the body releases larger amounts of cortisol, a steroid hormone which can raise blood pressure. In addition, the body releases catecholamines during stress which can also raise heart rate and blood pressures.
Different people respond differently to stress and therefore there is no way to predict if your mother's level of stress will effect her blood pressure. Plus, blood pressure is affected by so many other aspects of our lives (salt intake, family history, weight, smoking) that its hard to say for sure that reducing stress alone would return her blood pressure to normal. It is likely that lowering stress in her life would have at least have some level of benefit.
High blood pressure has detrimental effects on the heart, kidneys and brain. It doesn't really matter what the cause is. So if a person is stressed out and that causes their blood pressure to be high, the body doesn't care about what caused it.
I suggest you have your mother meet with her primary care physician
frequently until her blood pressure is under control. It will go a long way to prolonging her life. Good luck.