Not entirely sure but it may be that she manages to get out of her room there before you close the door. When you pull up the camera screen you can see where all the girls are. Check to make sure she is still in her room to the side of the hallway, if not she's probably out and ready to jump on you. Not sure if there's any way to put her back in there if she does got out but I'm also not sure if she actually leaves the room. If it does keep happening, and you know for sure she's in the room, then I would report it as a possible bug and see what the devs say.