Artist unknown, taken from here
Repost of a theory I posted to /r/asoiaf
Superficially, Cersei is the Mad Queen. Paranoid, with delusions of grandeur, and meeting more than enough criteria from the DSM to get a diagnosis of narcissistic personality disorder, Cersei appears to be Westeros’ answer to the cliche “absolute power corrupts absolutely.”
As Queen Regent, she has – or thinks she should have – absolute monarchical rule over Westeros and, more importantly, over the Great Houses and families that she thinks are beneath the glory of House Lannister. However, she lacks the skills, tools, and intelligence to be the effective ruler she wants to be, and her plans are all undone by her own paranoid attack on Margaery Tyrell, resulting in her own fall from grace and naked Walk of Shame forced by the High Sparrow’s crusade against the sexual and other largesse that Cersei represents.
But what else does Cersei represent in the world of Westeros?
How can we assess femininity in Westeros through Cersei’s warped world view?
And where does her madness come from?