It's not that the sister subplot is stupid, as it's not in and of itself. It is a believable turn of events. However, I think it was a dumbass move to go that route, as the first film was much more effective when Meyers was just randomly going after Strode for no apparent reason. The whole sister idea ruins the creep factor of this potentially happening to anyone. I've never thought the original to be as good as most people say it is, but it did have that strong unknown factor going for it. The sequel took that away.