>>68767239the joke is that she is pretending that the room she is in is stationary and the place where the visible wall is is just a long door which is sliding perpendicular to the actual room in which she is standing
once the long strip of "door" finishes sliding the "door" isnt completely aligned with the frame of the room because the sliding strip has gone too far past the bottom of the room which also furthers the implication that the room isnt actually moving and its in fact just the wall moving instead
at 18 seconds into the clip she acknowledges the chat comment about it actually being an elevator (completely missing the point of the joke she is making) and the "door" she is referencing just being the moving wall of the shaft in which the elevator resides and at 25 seconds when she reads the second comment she makes the concession that the joke didnt land and agrees with the chats impression that she actually thought it was a long sliding strip of door and she wasnt aware of it being an elevator
of course the entire time she knew it was an elevator and was making a very obvious joke to anyone who has a triple digit IQ but my oshis fanbase isnt very intelligent so it wasnt surprising whatsoever that they made those comments in chat