Can't buy Hjerim

Every time I talk to the steward at Windhelm, he says something has happened so I can't buy it. I know that I have to do the Blood on the Ice quest, but I did the the Dark Brotherhood quest where I had to kill Nilsine, so Tova committed suicide. But when I go to her room, her body isn't there. Whenever I go to the graveyard, there isn't anything there.

I've heard that I have to "enter and exit" Windhelm 3 times, but does that mean I have to actually go through the doors, or just fast-travel away 3 times?