You’re completely wrong. Virtually all residency programs are within medical schools. Her “boss” would be the head of a medical school department and his/her boss would be the dean of the medical school.
Sorry, you are in error. The medical school attending physicians may run the programs, but the residents (post graduates) are selected by the medical school department heads, but they are HIRED AND PAID BY THE HOSPITALS. I have worked at medical schools in my past life for more than 10 years. The medical school clinical staff train the residents, but they are no longer medical students. There are also hospitals that are NOT associated with medical schools that will hire residents and not all medical schools have their own hospitals. Also, keep in mind that once a medical student graduates from a medical school, they ARE PHYSICIANS and can practice medicine legally, as long as they have applied and received their state license. They do NOT have to wait until they complete their internship or residency to practice medicine. In fact, most interns and residency get 2nd jobs providing after-hours/weekend coverage at smaller community hospitals or doctors offices.