The grue appears! .... But I guess the little lantern and lightsaber are good enough light sources, so the group doesn't get eaten. For now anyway. .... And it's already got stomach troubles, so another point against that.

Is Pete metagaming here? Definitely. But it also seems that the GM is counting on that as the snake thing's just talking a lot and mentioning Rey and the sword. Which honestly probably makes more sense than the movie does; this critter kinda has wampa vibes with the teeth and the "personalized" cave it's living in. Why wouldn't the main characters try and immediately slice or shoot it, especially with how Poe's already pointing a blaster at it? It's not like there's an obvious exit to run away through. The really weird thing is that Rey really does appear to hand over the lightsaber to Finn.

Oh, and this thing definitely doesn't talk in the movie. It's too non-human looking to speak English Galactic Basic, and with a mouth full of teeth like that, I'd honestly be extremely surprised if it makes any sounds other than hisses or movie-rancor growls.