to rsvp you just send an ask. if you're unsure just let her know then, i doubt it'll be a problem.
as for what's going on, i don't think there's exactly a scheduled list of events. i know there'll be lots of dancing and hanging out, plus prom tier announcements, but beyond that i think we're just chilling. it's mostly a social event.
if you've got any other questions, the organizers are all really cool, if you just send an ask to the blog they'll get back to you.