Hypertension: Given the patient's age and significantly elevated blood pressure (190/100), hypertension is the most straightforward and likely diagnosis. The patient's blood pressure is significantly above the normal range, indicating either uncontrolled hypertension or a new onset of hypertension that needs immediate attention.

White Coat Hypertension: Although less likely given the severity of the elevation, it's possible that the patient's blood pressure is elevated due to anxiety or stress caused by being in a medical setting.
Medication-induced Hypertension: Certain medications can cause an increase in blood pressure. Given the patient's age, she may be on multiple medications, some of which could be contributing to her hypertension.
Sleep Apnea: This condition is common in the elderly and can lead to elevated blood pressure due to intermittent hypoxia and increased sympathetic tone.
Chronic Kidney Disease (CKD): CKD can cause hypertension due to fluid overload and activation of the renin-angiotensin-aldosterone system.

Pheochromocytoma: Although rare, pheochromocytoma can cause severe hypertension and would be catastrophic if missed. It's essential to consider this diagnosis, especially if the patient has paroxysmal symptoms.
Aortic Dissection: Severe hypertension can be both a cause and a result of aortic dissection. This is a medical emergency that requires immediate diagnosis and treatment.
Hyperthyroidism: Thyrotoxic crisis can present with hypertension among other symptoms. Given the potential severity of this condition, it should not be overlooked.
Renal Artery Stenosis: This condition can cause secondary hypertension due to decreased renal perfusion leading to renin release.

Cushing's Syndrome: A rare endocrine disorder that can cause hypertension due to excess cortisol production.
Primary Aldosteronism: A condition characterized by excess aldosterone production, leading to hypertension and hypokalemia.
Thyroid Storm: A life-threatening condition that requires immediate recognition and treatment, which can present with hypertension among other symptoms.
Coarctation of the Aorta: A congenital condition that can present late in life with hypertension, although it's extremely rare in a 96-year-old patient without a previous diagnosis.