Jon being a dumbass who doesn't know when to keep his mouth shut, plus
The Red Keep makes her sad
Equals "obviously time to methodically kill thousands of innocents?"

She was more upset about Jon blabbing to his sisters than she was about the man who raped her in S1 or the men who betrayed her, stole her dragons and tried to imprison her in Qarth?

Again, I buy her as a villain. But they needed to show us how they got from point A to point B instead of just dropping us off at point B and shrugging their shoulders while they speed off.