A 23-year-old woman is brought to the emergency department by her partner due to sudden, excruciating abdominal pain that began while she was engaged in high-intensity exercise. She describes a dull, intermittent right upper quadrant discomfort over the past few weeks that acutely worsened to a 10/10 severity. Her medical history includes a previous diagnosis of anxiety, for which she takes alprazolam, and she also reports regular use of oral contraceptive pills. She has recently undergone a significant, rapid weight loss in preparation for an athletic competition. On examination, she appears acutely distressed. Her temperature is 37.50C, blood pressure is 80/40 mmHg, pulse is 110 beats/minute, and respiratory rate is 15 breaths/minute with an oxygen saturation of 96% on room air. Her physical examination reveals an athletic build with prominent shoulder musculature, a broadened neck, and noticeable acne on her forehead and upper back. The abdomen is diffusely tender, with guarding and rebound tenderness most pronounced in the right upper quadrant. Initial intravenous fluid resuscitation has been initiated. What is the most likely diagnosis and the immediate next step in her management?