"There is something wrong,", Margaery says, heat pooling in her head. She knows something is wrong, acting out the next steps of the dance automatically, head miles ahead of her - why is Cersei away, why is Tommen away, where are they and what has Cersei planned Margaey hasn't accounted for.
She tells them to leave, to get away, gets her brother - precious and mutilated and a shell of his golden former self -, but they do not let her go.
Fear worms into her heart.
What has Cersei done, whatever it is - it is enough to make her fear for her own life, enough to not attend her trial, enough to make precious Tommen not attend as run in her mind. Possibilities run in her mind. Not even one sounds like something Cersei would do, but what does Margaery know? She hasn't predicted whatever this is.
Margaery finds herself reminding a line that she threw away what seemed a lifetime ago - "Perhaps I should let Joffrey choose. I'll end up with a string of sparrow heads around my neck." - and by the Gods, she wished she had one right now. Margaery is fully aware that wishing for a murderous boy king is wrong, but this entire farse wouldn't have gone so far with him wearing a crown - there wouldn't be a sparrow left on Westeros, had Joffrey become king, but there also wouldn't be anything else.
She looks at the High Sparrow, mustering all the hatred she can, noises of an explosion filling her ears as heat pools by her feet - and Margaery is fully aware that this is it.
Wildfire.
Her grandmother had told her fantastical stories about it, about a Targaryen prince who drank it on his tentative to become his family symbol, about its destructive power, about rumours of wildfire caches through King's Landing. Margaery just didn't think that the stories that had her captivated as a child would be her end.
Margaery thinks briefly about Tommen, the king barely more than a boy who loved her and that Margaery saw as, emotionally, not more than a brother, and looks at her own - bloody and broken and malnourished. Loras doesn't look at her.
She holds tightly into Loras, sees green, and then, sees nothing.