She certainly understands Cersei better than most and I think this is for having taken an active part in writing her. She has hinted at it before. Still, there are some things she says I cannot fully agree with.
Cersei does not hate Tyrion at the beginning, she dislikes him, yet she will behave as if she still wants him as a friend in S2 and S3. It is definitely a conflicted relation but hate is what Robert expresses when he speaks of Targaryens: "In my dreams, I kill him every night" or "I'll kill every Targaryen I can get my hands on". This is hate, not what Cersei says to or of Tyrion before Joffrey's death.
Then there is the usual discrepancy between an author's intent and an author's achievement, especially when that author is multiple as is the case here since GRRM's book original is being seriously altered.
When Lena says Cersei organised Shae's testimony at the trial, it may be what she tried to convey in her acting but as a viewer I must say this remained ambiguous. And it should be anyway because Cersei ought to have enough control of herself not to betray her manipulations and therefore act as if she heard the stuff for the first time. Well done on the acting side then, but not on interpretation. The show has given us this scene before between Cersei and Tywin in which he denies her the chance of even discussing the trial with her. It also has led us to think Shae was brought to Tywin after she was arrested and we must assume he would not allow Cersei to have access to her.
When Pod tells Tyrion a man he didn't know offered him a knighthood for a testimony, we may think it was Cersei's envoy but it could have been Tywin's or even Littlefinger's. Anyone can make false promises.
I find the interpretation that Cersei is sincere in her belief the better one. Did she try to buy Bronn? It could have been on Jaime's request in payment for his lessons and secrecy about them. Jaime will hire Bronn later, not Cersei.
So here we see that when all pieces come together a different understanding can be derived than one of the authors had in mind. The same happened with the infamous scene in the Sept. It was written and filmed as consensual but cut down to look like rape at a later stage, pulling the rug from under the actors' original understanding, so to say.
I also disagree with her statement about Cersei plotting against Margaery as a result of losing control over Joffrey. Cersei goes to her father and tells her about her justified concerns. This is not plotting. Then she stays put for two more seasons. Cersei will only start plotting against Margaery in S5 and apparently only in reaction to manipulation attempts on Tommen.
Cersei is a very passive, reactive character. She dislikes Margaery from day one but won't make a move until she feels threatened. She did the same with Ned, offering him a way out in spite of his knowledge. Tywin wouldn't have done that. "Why is he still alive?", he asked Jaime in their first scene together. In S2, while Tyrion is removing people and using Lancel, Cersei merely organises the defence of the city. She only goes after Tyrion once she thinks he is endangering Joffrey's life. Cersei doesn't plot very much or very well. She fights back and does it at the last possible moment.
