In A Feast for Crows Cersei learns that Dragonstone has been retaken, but that there were great casualties. In particular, she is happy that Ser Loras has been gravely wounded in the battle. She did not like the undue influence he had over Tommen, and Cersei did not like that Margery's brother (Loras) was in such close proximity to his sister (to keep her safe and on a short leash). With him removed Cersei is sure that her plan to discredit Margery will happen.
