I absolutely loved this ;). The best part had to be Jaime laughing uncontrollably in the background.

And this passage: "Her fingers tighten around the stem of her goblet, and she considers how satisfying it would be to launch this one at Jaime’s head, then to grab Stannis’s untouched glass and fling it at the sullen, solemn, damnable Master of Ships."

This is so like Cersei, who can't stand being beaten at anything. You captured her character really well, for of course she'd take it as a challenge to use her charms to try and persuade Stannis of something.