I think she's the oldest of everyone going (god she's like twenty now gross) so she'll probably end up being a bit of a mother hen, although a... good natured one. She won't entirely be relaxed but she's really good at pretending to be! So everyone will be treated to friendly and sociable Steph who's just secretly expecting something to go horribly wrong.

She will probably bring sensible food to accompany all the junk food and is armed to the teeth but hopefully no one needs to find out about that.

Mostly she will just offer to braid people's hair and make fussy gestures at them if she thinks they're getting dangerously close to the fire.