Hannah did say: "You should've killed me", she knew exactly what she was going to do.
I knew that the release of that mob lord was fixed.
Also, next episode. Due to seeing Doukes, I think some of the scenes shown as preview are, memories/dreams/thoughts/fantasies/etc. something like that to deceive us and get our adrenaline pumpn for it

One things for sure, if Hannah remains alive along with that mob lord, Dexters life along with Debs becomes quite difficult.