I guess not being appointed Listener of the DB got under her skin over the years.
That's probably it. I finished the Brotherhood quest line for the second time yesterday and her flaws only became more apparent. Cicero attacks her because he overheard her saying negative stuff about him and the Night Mother and when I am back at the sanctuary she says that
I must deal with the situation she caused and find her lost husband while at the same time telling me that the whole idea of me being the Listener is silly. Then after I kill Cicero (I actually spared him this time around) and bring her husband to safety, she chooses to betray me during the emperor assassination quest. So much for the whole "respect your family" business she has going on in the Brotherhood.