Why isn't that the dream she mistook for reality and got hung up on?
I was about to say, any other manga would get away with this as a silly bonus, but in this one it undermines the premise a little :P
it doesn't, because happy dreams like that are totally just horny self-serving fantasies, while anything painful obviously has to be 1000% true, precisely because it hurts so much it can't not be true, or so the logic goes