Hypertensive Crisis: Given the patient's significantly elevated blood pressure (167/111 mmHg) and symptoms of chest tightness, a hypertensive crisis is the most likely diagnosis. This condition can lead to cardiac and vascular complications if not promptly addressed.

Anxiety or Panic Attack: Chest tightness can be a symptom of anxiety or panic attacks, especially in young adults. The negative troponin helps to rule out acute myocardial infarction, making this a plausible diagnosis.
Pulmonary Embolism: Although less likely given the absence of other typical symptoms (e.g., dyspnea, tachypnea), pulmonary embolism should be considered, especially if there are risk factors such as recent travel, immobilization, or family history.
Acute Coronary Syndrome (with negative troponin): While the troponin is negative, it's essential to consider acute coronary syndrome, especially if the chest pain is suggestive of ischemia. Repeat troponin levels and further cardiac evaluation may be necessary.

Aortic Dissection: This is a life-threatening condition that requires immediate diagnosis and treatment. Chest pain and hypertension are key symptoms, and even though it's less common in young women without known risk factors (e.g., Marfan syndrome), it cannot be missed.
Pulmonary Hypertension: If the patient has a history suggestive of pulmonary hypertension (e.g., connective tissue disease, history of pulmonary emboli), this diagnosis should be considered, as it can present with chest tightness and hypertension.
Cardiac Tamponade: Although rare, cardiac tamponade can cause chest tightness and hypotension, but in the context of hypertensive crisis, it might be masked. It's crucial to consider this diagnosis if there's a significant change in clinical status.

Thyroid Storm: This condition can cause hypertension, tachycardia, and chest discomfort. Although rare, it's essential to consider in patients with a history of thyroid disease.
Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodic hypertension, tachycardia, and chest pain. It's a diagnosis of exclusion but should be considered in young patients with severe hypertension without a clear cause.
Spontaneous Coronary Artery Dissection (SCAD): A rare cause of acute coronary syndrome, more common in young women without traditional cardiovascular risk factors. It should be considered, especially if there's ongoing chest pain suggestive of ischemia.