To knock your husband by the door: in fact, it is a lightweight, especially if the door is 60 cm wide. I am not a fucking strong person, but I easily translated dozens of doors with glass in my warehouse. The main weight in them is from glass, the rest of the cardboard weighs a maximum of 3 kilos. And the fact that the original door is cardboard, is confirmed by the fact that your cousin broke it in the place of attachment of the cock.
The only difficulty is to knock that door in the hallway. Therefore, I believe that your sister pulled out this door, moved her husband frontally and continued to extinguish him in the same direction.