Winter quotes an interview with Diana Rigg, in which she talks about playing Olenna. One of the things she says about her character is that she’s “pretty evil.” Dan Selcke responds:
Rigg may have been speaking with her tongue planted in her cheek, but that’s one way to read Olenna’s actions. She did commit regicide, albeit against someone few would miss. But generally speaking, Olenna’s motives are sympathetic, even if she’s done some questionable things in the name of her family’s well-being.
I don’t think Rigg was speaking tongue-in-cheek at all. Lady Olenna is at best a deeply, morally ambiguous character. We like her because it’s so much fun to watch her rip into Cersei and say horrible things about her male family members, but still, we’re talking about someone who’s been in cahoots with Littlefinger.
It’s one thing to kill Joffrey; that much needed to be done. And we can sympathize with Olenna for wanting to protect her granddaughter. She was conspiring with Littlefinger, though! They didn’t even try to make his death look like an accident; oh no, they let Tyrion take the blame, and by extension they put Sansa on the wrong side of the law. Olenna knew what was going on when she snatched that gem out of Sansa’s necklace at the wedding feast. She seemed to be sympathetic to Tyrion, and she acted like she gave a fuck about Sansa, but when the time came to get rid of Joffrey, she knowingly allied with someone who fully intended to put an innocent man on trial for his life and abduct an orphaned girl.
It didn’t end there, either; she knew Littlefinger was involved in Loras’s arrest by the Faith Militant, and she still conspired with him to get Cersei arrested. And, again, it’s understandable that she’d want to put Cersei in the hot seat, but she’s still working with the most morally corrupt man in the known world.
Through all this, her motive was to protect her family; fine. She loved her grandchildren and wanted to see them survive their alliance with the Lannisters; fine. Maybe, we can even argue that it’s natural for her to be willing to sacrifice innocents from other families in order to save her own. Natural, but still incredibly destructive. She did all this by conspiring with Littlefinger, of all people. Now that her son and his children are dead, what excuse does Olenna have anymore? Now she’s willing to get into bed with the goddamn Sand Sucks, and how much more fresh fuckery is she prepared to unleash until she feels like justice has been done?