The problem with saying one of the Denerians is responsible for whispering to Dresden is the simple fact nothing they do qualifies as cheating. They exist in balance with the Knights and are free to maim, deceive, kill, and subvert to their black heart's content. Another reason to exclude the Denerians is because something so subtle would not really be practical at that moment and time for them. If they wanted him dead and managed to get that close to him, then why waste the breath? Just bash his head in and be done with it. As for Lash specifically, assuming that she even survived giving up her 'life' for Dresen, what would she gain by getting Dresden to kill himself? The entire purpose of the Shadow of Lasciel is to subvert Dresden so he will take up the coin; killing him would be quite counterproductive.

The truth is that Uriel's care to avoid saying the Fallen's name makes it clear who he is talking about. Think about how in Small Favors, Mab takes great care to refer to the archangels by titles and not by names, even cautioning Dresden about saying Uriel's name. How in Changes, the Erlking warned Dresden about the consequences about saying Mab's name a third time. To put all that it into context, the idiom "speak of the Devil" is more than just a turn of phrase in the Dresdenverse, and quite literal in this moment and time. It was the Prince of Darkness cheating in Small Favors that dragged Uriel into the story, and it seems the Prince of Darkness cheating in Changes dragged Uriel back in again.