Because she chose the location. She's convinced that if she chose someplace else, it wouldn't have been so bad. He's got her completely twisted into thinking that corrupting itself would have been all right because it helps him. She thinks he's her friend.

[ Even more than him. Which does hurt, given what Elias has done to his friends. ]

I don't think it's entirely her fault either. But her alliance with him has become dangerous. For her as well. She could have been killed while she was acting as his damned conduit. And the only thing he would have cared about is that one of his sanctums was destroyed.