There is definitely an argument that Margery Tyrell (Daughter of Lord Mace Tyrell, grand-daughter of Lady Olenna) is one of the savviest individuals who is top-notch at playing Game of Thrones. She was the bride of Lord Renly Baratheon when he had a tremendous amount of power and wealth, once Renly was killed by the shadow monster created by Melisandre, she switched her allegiance and scored the ultimate prize. She became the Queen after Tyrells bailed out Lannisters from the attack by Stannis’s forces in the Battle of Blackwater Bay at Kings Landing. [Technically it was Tyrion’s wildfire idea which crippled the Stannis’s entire fleet and saved the kingdom]
She is, in fact, better than her counterpart Cersei Lannister in many ways. She is married to her son Tommen, on one hand she has successfully manipulated him to her advantage while on the other hand he is beyond the influence of Cersei now as he is surrounded by warrior’s sons (former Knights/noblemen who renounced their houses and joined the faith militants) who form his Kingsguard. Cersei Lannister went through “walk of shame”, and when the time came for Margery to atone for her sins, suddenly King Tommen appeared and declared holy alliance between church and the Crown. While Margery is standing on the steps, she is totally calm and composed as if she has planned the whole thing. It’s quite possible that Margery is playing a game of thrones as her new-found religiosity is hard to digest.
In the previous episode, she met Tommen and told him to cooperate with High Sparrow who helped her cleanse her soul. If you remember, there is a scene in season 4 where Lady Olenna is helping Margery choose jewelry for her wedding to Joffrey and she makes a joke about wearing a necklace of “dead sparrow heads”. Do you really think Margery of all people would fall by the wayside and allow a religious zealot like High Sparrow to call the shots?