Re: Batman Begins v.s The Dark Knight Rises
I can see where Talia was coming from. She hated Ra's for throwing Bane out of the League. Then he's gone, and she can't reconcile with him. Before Bane found Gordon's confession, he had been recruiting Gothamites that were put out of work. Talia had been in Wayne Enterprises for an unspecified number of years, and would have seen corporate greed as the source of job losses in Gotham. That would allow her to line her goals up with the League's purpose. I believe that Talia fixated on Gotham because it was the city where her father was killed. So completing that mission for him would make sense, in terms of honoring him.
"I defeated your uncle Victarion and his Iron Fleet off Fair Isle, the first time your father crowned himself. I held Storm's End against the power of the Reach for a year, and took Dragonstone from the Targaryens. I smashed Mance Rayder at the Wall, though he had twenty times my numbers. Tell me, turncloak, what battles has the Bastard of Bolton ever won that I should fear him?" - Stannis Baratheon