At around 5 minutes in during a scene in the mess tent Nurse Donovan can be seen getting up from the table, the camera angle changes and she gets up from the table a second time.
Donovan asks BJ to meet her in her tent. It is highly unlikely that she would have her own tent and not be quartered with the other nurses.
B.J. gets up from the mess tent with Nurse Donovan table and walks out the door. After the door closes, he is still standing in place, not actually leaving the scene.