[Olenna Tyrell — Characters]
Daenerys showed herself to be quite vengeful on several occasions, mainly to individuals who had caused her significant grievances. When Mirri Maz Duur tricked her into allowing the use bloodmagic to "save" Drogo, Daenerys had the witch bound and burnt alive. Upon learning the role that Xaro and Doreah played in the theft of her dragons (and the deaths of her servants), she had them both locked in an empty vault. She had Randyll and Dickon Tarly burned alive for refusing to bend the knee after she defeated them in battle, which may have further soured her reputation in Westeros along with Cersei's anti-Daenerys propaganda. In the last case, however, it is worth noting that she executed them only after offering them the choice of surrender, which they declined. Tyrion also seemed to believe that her execution of the Tarlys was more the result of losing her temper, rather than any deliberate ruthlessness. Also, her refusal of listening to Tyrion in that moment could be caused also by both her anger against his military failure and by Olenna Tyrell's advice about learning to take decisions by herself.
Lady Olenna Tyrell explains to Tyrion that House Tyrell will support the cost of the wedding between Joffrey and Margaery. Following this, Lord Tywin summons both Tyrion and Cersei to his chambers to inform them of his plans to wed them off, Cersei to Loras Tyrell and Tyrion to Sansa Stark, who Tywin explains will be heir to Winterfell after he defeats Robb Stark, thus giving the Lannisters a future foothold in the North.
Jaime reveals to Cersei that Tyrion is innocent of Joffrey's murder, telling her Olenna Tyrell confessed to it. Cersei is dismissive, so Jaime talks her through it, asking her rhetorically if Olenna would prefer Margaery to marry the strong willed and sadistic Joffrey or the emotionally pliable and good-natured Tommen. Effectively, Olenna would have become the true ruler of the Seven kingdoms behind the scenes - in the same way that their father Tywin Lannister became the true ruler of Westeros through his grandsons.
All of this points to another mistake outsiders often make, Ned Stark for example, when dealing with Cersei as Olenna Tyrell noted before her death: failure to imagine just how far Cersei is willing to go to keep her power.
A key difference between Cersei and Jaime is that Cersei honestly believes, in her skewed view of the world, that she is "good", Joffrey is a great king, and all of her enemies are "evil" people trying to destroy her and her children. In contrast, Jaime does not maintain any pretense of being a "good" or honorable man, as he has become apathetic to such concerns - this was influenced by him being hated and loathed by everyone because he killed a man who had infamously terrorized the Seven Kingdoms, opening his eyes to how people perceive goodness and honor. However, he still has some respect for the rules of engagement, as he refused to kill Ned Stark when their duel ended abruptly, since Ned was incapacitated by an opportunistic guard rather than Jaime himself - Jaime personally punished that guard seconds after the duel ended. Jaime also was capable of treating his own enemies rather respectfully, telling Ned Stark that his father and brother didn't deserve to die the way Aerys killed them, and saved Olenna Tyrell from a crueler fate that Cersei would have inevitably given her, by allowing her to die painlessly.
Sansa discusses the possibility of Littlefinger being in love with her, but Shae warns her that Baelish is manipulative and men usually want "one thing" from young ladies. Margaery and her grandmother Olenna Tyrell invite her to lunch in the gardens, where they ask her about Joffrey, after being escorted by her chambers by Loras. Sansa is initially too fearful to speak the truth, but eventually breaks down, her eyes blazing, and angrily recounts how Joffrey had said he would show her father mercy, only to behead him in front of her, and how he then took her up to the wall and forced her to look at her father's head on a spike. Sansa nervously attempts to backtrack, but Olenna tells her that they will never betray her confidence. Sansa admits that Joffrey is a "monster."
Typically, if a noblewoman marries above her station into a more powerful family, she will switch to publicly using that family name. For example, " Olenna Tyrell " was born Olenna Redwyne, but the Tyrells are the Redwyne's overlords so she switched to use of that name. A noblewoman who married below her station would defiantly continue to use the name of the more prestigious family she was born into.
Daenerys agrees to their terms in return that the Ironborn cease raiding, pillaging, and raping the mainlanders. Yara is reluctant at first but assents to the agreement when Theon gives her a nod. Some time later, Theon and Yara begin the voyage back to Westeros with Daenerys and her retinue, along with the Iron Fleet, the Dothraki, the Unsullied and the armies of House Tyrell and Dorne, with Ellaria Sand and Olenna Tyrell having heard of Theon and Yara's actions and followed them in declaring for Daenerys.
Joffrey, Margaery, Cersei, and Olenna Tyrell are visiting the Great Sept of Baelor , where the royal wedding will be held. Joffrey tells Margaery about the history of the dead Targaryen kings, pointing out Aerion Targaryen in particular and gleefully recalling how he thought drinking wildfire would turn him into a dragon. When they hear a crowd of smallfolk outside Margaery suggests they greet them; Joffrey is reluctant but has the doors opened. Joffrey and Margaery step outside to a happy, cheering crowd, while Cersei looks on angrily.
During the Sack of Highgarden , Jaime confronts Olenna Tyrell and Olenna notices Jaime is carrying Joffrey's old sword, Widow's Wail. She calls Joffrey a c*** and later informs Jaime that it was her who murdered him, after she herself imbibes poison provided by Jaime. She remarks that she didn't know how vicious her murder of Joffrey would end up being, and to tell Cersei that it was her who did it.