I think its like Zedar said before, killing Hazama would be useless because of his life link and the fact that "Hazama" is simply the body he is using atm, and if it dies Terumi can just get another. In order to kill Terumi, they have to kill him as in, not Hazama but Terumi himself, which Hakumen did in CP.
In CS, I'm pretty sure Rachel didn't take into account that Hazama established a link with Noel and was completely caught off guard by it.