The_Blue_Rider said:
But its completely understandable, her way is what allowed the Brotherhood to survive all these years
There's an argument to be made that the Brotherhood
hasn't survived; what exists now is just a group of thuggish hired killers, similar to the Brotherhood in name only, and even that's dwindling! The Brotherhood had something deeper to it than simply killing for money. With that in mind, can we really say that Astrid has kept the Dark Brotherhood alive, or has she simply remade it into something else?
The_Blue_Rider said:
and suddenly Cicero and the Night Mother show up to return the Brotherhood back to how it was, she'd understandably feel betrayed, especially with the knowledge that members of her "family" were supporting Cicero as well. By killing you she would ensure that the Brotherhood would never return to what it originally was.
The snag there is that, prior to you being named Listener, she seems to respect and even fear the Night Mother. Other members of the sanctuary are receptive to a return to the old ways. I didn't get the impression that it was returning to the old ways that frightened her, it was losing her grip on the reins and becoming subservient to someone else. After all, why wouldn't she want the Brotherhood to return to the glory days? Feared and respected across all Tamriel, able to dictate the fortunes of an empire by who they do or do not kill. Why would she rather be a gang of brutes living in a grotty cave when she could be that? We've already seen, in her quick enthusiasm for the Big Kill, that she wants the Dark Brotherhood returned to glory. She just wants to be in control when it does.