Everyone’s situation is different. Your Sister’s is an especially difficult case. She should raise this issue with her fellow staff. Since Medical Personnel and First Responders have unique needs, the hospital should devise a plan wherein the staff would know who’s required to be on duty and for how long. IF they are going to require your Sister to hang around until it’s too late to evacuate, they need to arrange some type of evacuation – especially given that your Sister and her co-workers are personnel with crucial skills.
Let’s hope that all Hospitals, Cities, Schools, etc. learn from both Katrina & Rita and immediately start brainstorming some of these problems.