A 42-year-old woman presents to the emergency department with intermittent right upper quadrant abdominal pain for the past two weeks. The pain is sharp, occurs mostly after meals, especially fatty foods, and radiates to her right shoulder. She reports mild nausea but no vomiting or fever. On examination, she has localized tenderness in the right upper quadrant. Her vitals are stable, and laboratory tests show mildly elevated liver enzymes.
What is the most likely cause of her symptoms??