I found the scene pretty disturbing too, to the point I had to rewind and stop-motion it to confirm. She's swallowed alive (the teeth clamp onto birdyface, which means she's held in the gullet already) - a horrible scene, and one weirdly played out to two watching kids who find it morbidly 'cool', which strikes me as attenuated writing. Reality check: the characters would need to be sociopathic not to be marred for life, but hey the audience laughed it off, thanks to a jaunty soundtrack (might as well throw in some canned laughter). It kinda shows the sheep-like manners of a crowd and the ability of an audience to be led.
Her crime was being snooty and unsmiling btw, set up for her comeuppance throughout the film, and the most heinous of crimes for a young, pretty woman.