Applejack stopped near where she thought Applebloom's door was, and kicked out. The house rattled as drywall crunched beneath her hooves. She had missed the door and hit the wall because she couldn't see where she was or what she was kicking due to her blindness, as has previously been established.
She heard a thump and a squeak, and then Applebloom spoke out. "Howdy, Sis. Looks like I can't see today. Do you think I could get an echolocation cutie mark?"