Mr. Green
Super Freak
Sansa knew Little finger was up to something. When he mentioned Brienne being honor bound to intercede it was him hinting to her that if she wanted to get rid of Arya she would have to send Brienne away first.
She played along with Little Finger so his guard would be down. Brienne gone? Check. Sansa paranoid about Arya? Check. They were playing him the whole time but had to wait for an opportune moment.
I like how it went down but it seemed too short. Little Finger crying and begging for his life was pathetic. Seemed out of character. Should have been a bit more argument but I need to watch it again.
Sometimes begging and being pitiful works. Sansa was on the ground crying her heart out way back, before Joffrey. Extreme circumstances requires extreme acting? LF was being charge with everything that he did, all in one or two minutes. And there is no time to strategies. The shock in his face is priceless.