If it is true that Brad, Sarah and Troyzan are the final three. I can jolly well see why Brad doesn't win over Sarah.
Hali believed she was with Brad and Sierra. They assured her that she's with them... and then turned on her. Half the time people don't realise the first thing you don't do is to say you won't vote for someone then turn your back on them.
Hence Cirie's alliance can't even approach Hali cause they thought that she was with them.. and since they're targeting her. Better her than them. Although they could have let the cat lose and try to recruit Hali as one of her own, but I believe Cirie was looking at the big picture that if it's not her, it would be Michaela and she'll rather keep the latter.
I wished we have enough time to watch all these unfold.