Sarah, a 55-year-old woman, visits her primary care clinic for a routine check-up. She has a past medical history of hypertension. During the visit, her blood pressure is measured, and the nurse notes it as 200/79 mmHg. Sarah reports occasional headaches but denies any chest pain, shortness of breath, or dizziness. She mentions that she has been under stress lately due to work and family responsibilities. Based on her blood pressure readings and symptoms, the nurse suspects that Sarah's hypertension may be progressing. Which stage of hypertension is Sarah likely experiencing based on her blood pressure reading and symptoms, and what is the most important action for the nurse to take?