This was something I thought more people would ask about. I thought it would cause some people think poorly of the comic. But I decided that without the door open, Apple Bloom wouldn't have woken up, so I needed the door open. And in the 'Cutie Pox' episode, they used the very same plot device. Applejack is woken up by Apple Bloom's uncrontrollable hoof tapping, both their doors are open. Albeit, not as open as AJ left Apple Bloom's door here in my comic, but I reasoned that she was tired and just assumed Apple Bloom was sleeping deeply.