A 19-year-old woman with anorexia nervosa, restricting type, presents with a BMI of 15.2, resting heart rate of 48 bpm, blood pressure of 88/54 mmHg, and serum potassium of 3.1 mEq/L. She has been in outpatient treatment for 3 months with no weight gain and eats approximately 600 calories per day with compulsive daily exercise. She denies suicidal ideation. According to APA guidelines, what is the most appropriate level of care?