[X] [Try and talk her down]
Switching my vote as I'm genuinely curious has to how Shirou would talk his possessed girlfriend down. Appeal to her sense of right and wrong? That doesn't appear to be in full working condition going by her family, but she might've gotten them before they could say anything. Could also point out the two servants are on their way to him, plus Circe. Not sure how powerful she is right now, but I don't fancy her odds in a three-on-one. More if his sister gets involved. Speaking of, this probably won't get her into the good books of said sister, nor of Taiga and her farther, who are pretty much family. Which is a problem for future dating prospects. Now sure, those are kinda odd concerns in this situation, but might hit more to this kinda odd Ayako.
He could also hit her with his own hero complex. That probably wouldn't work, but who knows?