Sorry to hear about your mother's fluctuating blood pressure.
I think that stress could be playing a role in your mother's abnormal blood pressure. However, from what you describe medical therapy will be a necessity. I would also recommend investigating techniques for relaxation and stress management. Regular exercise may also help improve blood pressure control. You may consider purchasing a home blood pressure monitoring kit, which will allow you to keep a log of your mother's blood pressure. This will help her doctor in managing the blood pressure.
Thanks for your question,
The doctors should check her for a Pheochromocytoma, which is a tumor on the adrenal gland. A prime symptom is fluctuating high blood pressure.