"No, incompetent enemies like Cersei are easy to deal with, albeit a bit unpredictable. She singlehandedly harmed her sons" cause far more than anyone else. She supposedly fell from the balcony into the Sunset Sea. I think that even the Kingslayer probably had enough of her foolishness and killed his lover and sister. Without her, there's a chance that someone capable will take the reins of House Lannister, which would be fine if they were our allies, but they are not," Olenna explained heavily and opened the second letter.