There's also no guarantee that she wrote the symbols down correctly, so we have basically nothing to do go on at this point.
Also, IIRC, the demon lord's name was supposedly Devilroi, which isn't even really French. Roi would be king in French, but devil isn't a word in French. Devil in french would be diable. So, it's a mishmash of languages.
From what happened with the object that showed up in volume 6, whatever system was put in place pretty clearly understands multiple Earth languages and was prepared to handle multiple Earth languages. So, who knows if the monolith is even displaying a single language, and if it is, it could easily be its own thing even though the obvious assumption would be that it was kanji or similar just because then Souma would recognize it if he had the chance to actually read it.
They've dropped major hints that the planet where the story is taking place is somehow related to Earth (be it Earth itself, a colonized planet, an alternate version of Earth, or whatever), and language plays a factor into that, but we've been given so little to go on in general that we can't do much more than speculate.