If Daria's wrong, Mariam is going to murder her. Well, if she's wrong that's probably the least of her worries, but somehow it manages to loom large in her internal calculus anyway.
She's not wrong. Look, she doesn't care how persuasive demons are supposed to be, unless they can literally do magic with their voice or something, nobody's going to talk her out of her soul. Probably. She hopes.
She checks the binding for the third time, makes absolutely sure there's nothing the demon can do if she doesn't agree to a deal. Nothing sticks out to her as a mistake. After a moment's thought, she grabs a spare sheet of paper and writes in big block letters
YOU PROMISED YOURSELF YOU WOULDN'T SELL YOUR SOUL
IF YOU'RE THINKING ABOUT IT DON'T
IT'S STILL A TERRIBLE IDEA
and tapes it to the wall behind the circle. She checks the binding over carefully for a fourth time. There's one line left to complete the cirlce - she fills it in and takes a cautious step back.