I don't understand the hate for this film (spoilers)

I thought it would just be a re-hash of the first one but they actually managed to keep the story fresh.
I do wonder about the ending though, has she found an inner serial killer in her from time spent doing the interviews and maybe watching his videos (which would explain the whistling), or has he somehow survived? I think im leaning to the former as why on earth would she let him live? If it were me id at least tie him up until the police got there and arrested him.