Writing about Melisandre, stannisisthefury says
she was the one who actually killed four of the five Kings, even if they did die from other hands (or maybe it was coincidence, but if any of the many Gods of Westeros have proved they’ve got actual presence, it’s R’hllor)
I think the answer, which I believe I gleaned from Stefan originally, is “neither.” She saw the deaths of Balon, Robb, and Joffrey in the flames, and concocted this dog and pony show with the leeches and Edric Storm’s blood in order to convince Stannis that the ritual caused the deaths, while it was in fact the other way around, basically. Whether she believes it or not is actually a good question — she does believe that the future can be changed (though she’s wrong, at least as far as her visions go; they always come true), so she probably believes she can push the future in the right direction, a direction it wouldn’t go if not for her pushing. But a wise man once said that theatricality and deception are powerful agents to the uninitiated. But you and I and Mel are initiated.