After visiting one sibling, Jaime is called to meet the other, a.k.a. the one he sexually assaulted last week. Meeting in her chambers, Cersei berates Jaime for only posting one guard outside Tommens door. She questions why Catelyn Stark set him free, to which he responds it was so they would send her daughters back to her. Pointing out that this means he made a vow to Stark, Cersei questions his loyalty and asks if she ordered him to find Sansa and kill her, would he do it? Before he can answer, she asks how he could go visit the monster that killed their son. Jaime insists that Tyrion didnt do it, but she says that he would kill them all if he had the chance. Before ordering her brother away, she demands that four men be posted outside Tommens door. Cersei is obsessed with seeing Tyrion executed for killing her son, regardless of whether he did it or not. Shes always hated him, and rather than find the real culprit, shes channeling her grief into making sure Tyrion suffers. Since almost everyone else in Kings Landing doesnt like Tyrion, they dont mind seeing him punished. Jaime is one of the few people who can look at this rationally, but as we saw, he wont be able to change Cerseis mind. Shell have her revenge on the Imp one way or the other.