This story is shaping up great! Also, a pair of ideas for this or another story if you want to use them. This setting lends itself for the imagery of aromatic steam coming out the girl's mouth and nostrils (with her either alive or dead, preferably the first option) and her girlfriends going for a flavorful french kiss with her. Also, you could try to keep Penny alive longer (perhaps even to the end) by giving her icy water to drink and lower the temperature of her internal organs while her meat cooks on the outside.