[Kevin]

Again, because it deserves repetition, she doesn't get to wear the badge until y'all are at least engaged (at least according to the governing documents of Sigma Nu).

Aside from that, it's nothing binding, but that sweetheart pin is usually something only worn by the current and former chapter sweetheart, not individual girlfriends or fiancées. That's how my chapter treats it. I'm pretty sure that's open to interpretation though.