Why did Graendal kill Asmodean?

So Graendal had the knowledge of what Asmodean was, he knew her and his killer, he feared his killer as he would another Forsaken, Asmodean felt a shiver right before dying that could have been a woman channelling and Graendal had not only the means to get to Caemlyn quickly, but to kill him.

Who killed Asmodean in the fires of heaven?

The Glossary of Towers of Midnight says of Graendal: “A ruthless killer, she was responsible for the deaths of Aran’gar and Asmodean and for the destruction of Mesaana.” In the book itself, Shaidar Haran states that Graendal’s actions have led to the deaths of three Chosen: “Three Chosen, destroyed by your actions.” …