Alysanne Snow

Personally, I much prefer show Cersei and I'm pretty sure she was just sucking up to Mace through Marg and will be back to opposing the wedding as soon as it is convenient for her. I don't mind them giving her some shreds of actual competence, as the book version bordered on a pretty offensive caricature at times. She's still a terrible human being, but one with an actual shot in hell of getting what she wants.