I am not doubting that Cersei is cold hearted. I'm saying that originally she didn't want any of this.
Cersei had no choice to take the throne because her children were all killed. If she could have they would have ruled forever as she wanted. She did everything she could to protect her children, Jaime and her family. She has to be the way she is because she has many enemies and they all want her dead. They will not reason and they won't stop until they get what they want.
Triggerfinger killed Jon Arryn which kicked off the events of Game of Thrones, she was wed to a man who never loved her and also beat and cheated on her every chance he could get because his first true love died loving Rhaegar Targaryen, Jaime pushed Bran out a window, Tywin killed Robb and sent men to spy on and kill Danearys, Tywin and Triggerfinger conspired to get and keep the Boltons as Warden's of the North and Walder Frey wealthy. Triggerfinger and Olenna are the ones who killed Joffrey and because of Tywin's hatred of Tyrion, in the end it got Myrcella killed because Oberyn Martell elected to be his champion and lost which led to Ellaria Sand killing Myrcella out of spite. She did everything to protect Tommen who appeared to be destined to be a good king until her killed himself. Remember it was also Tyrion who sent Myrcella off to Dorne in the first place to protect his niece and spite his sister. It was also Tyrion who killed her father who might have been the only person capable of protecting her family. And we wonder WHY Cersei is the way she is ??? Go back and watch seasons 2-5 she said she didn't want any of this.
Now it has all caught up to her and she has no choice but to fight because her opposition obviously won't. But the vast majority of the shit wasn't even her beef to begin with. But she's the one who has to deal with it.
