The king had been her last hope. The king could command Father to let her stay in King's Landing and marry Prince Joffrey, Sansa knew he could, but the king had always frightened her. He was loud and rough-voiced and drunk as often as not, and he would probably have just sent her back to Lord Eddard, if they even let her see him. So she went to the queen instead, and poured out her heart, and Cersei had listened and thanked her sweetly... only then Sir Arys had escorted her to the high room in Maegor's Holdfast and posted guards, and a few hours later, the fighting had begun outside. "Please," she finished, "you have to let me marry Joffrey, I'll be ever so good a wife to him, you'll see. I'll be a queen just like you, I promise."
Queen Cersei looked to the others. "My lords of the council, what do you say to her plea?"
The poor child, murmured Varys. "A love so true and innocent, Your Grace, it would be cruel to deny it... and yet, what can we do? Her father stands condemned." His soft hands washed each other in a gesture of helpless distress.
A child born of traitor's seed will find that betrayal comes naturally to her, said Grand Maester Pycelle. "She is a sweet thing now, but in ten years, who can say what treasons she may hatch?"
No, Sansa said, horrified. "I'm not, I'd never... I wouldn't betray Joffrey, I love him, I swear it, I do."