I thought through this season and thought that Dawn MAY have a shot at winning had she not blindsided Brenda that early. You see, if that night Eddie had went home, Erik will be medivac next. That means Brenda will be in the F4. And at the F4, if Dawn votes out Brenda, it would be seen as one of those moves where the jury understands and accepts because well, Brenda will win the million if they bring her there, so I think, even Brenda would have accepted the move to vote her out at the F4 graciously (that's if she doesn't win both IC and RC).
Considering that Brenda was blindsided at the F6, at ponderosa, the Survivors get MANY DAYS and OPPORTUNITIES to discuss and find out what happened from one another.. and that's one factor of the game that people cannot forget. Whatever you do in the game... those people you vote out... they are going to go to Ponderosa and discuss about it. If they catch you lying, you're probably dead.
I think Brenda went to Ponderosa and the whole world was sorry for her, thus all the votes were swayed away from Dawn, even if (really) people like Malcolm thought she played a good game and initially wanted to vote for her.