The idea of Deb poisoning herself did occur to us, but we quickly concluded that that's just not Deb. She's smart enough to think of it, sure, but it's just not the way her mind works. She is the mirror image of Dexter: Dexter lives on the inside where no one can see the real him, and Deb lives entirely on the outside where you can't help but see her. This kind of deception is not her. Now, admittedly, since her promotion she's been forced to learn a bit about keeping things inside and being sneaky; and admittedly, the writers aren't always so consistent about stuff like this when the plot demands it. But it just didn't fit, and I was glad to see them be overt about confirming Hannah did it.