A 28-year-old G2P1 woman at 34 weeks gestation presents to the outpatient clinic with a 12-hour history of escalating right upper quadrant pain, now radiating to her right shoulder, which started after a meal rich in fats. She reports associated nausea and several episodes of non-bloody emesis. The patient also complains of subjective fever and chills. She denies any hematemesis, dyspnea, or lower extremity swelling. On examination, her temperature is 38.80C, blood pressure is 115/75 mmHg, pulse is 108/min, and respiratory rate is 22/min. Oxygen saturation is 97% on room air. Her BMI is 31 kg/m^2. Fetal heart rate tracing in the clinic demonstrates a reassuring baseline rate of 145/min with moderate variability and no decelerations. Abdominal examination reveals marked tenderness in the right upper quadrant with both voluntary and involuntary guarding. During deep inspiration, palpation of the right upper quadrant elicits an abrupt cessation of breath. Cardiac examination reveals a benign flow murmur. Pulmonary examination is clear to auscultation bilaterally. Given this presentation and the laboratory findings, what is the most likely diagnosis and the appropriate initial management strategy?