You know... that Tri-Ess thing sure does sound like a sorority... just a really really peculiar one. They have social events, they have a Big sister program... haha.
No offense to the Tri Sigmas out there! I can definitely understand why you would want to make it clear that you are not affiliated with them.
Anyway... I have seen a girl on my campus wearing ZTA letters, and I always want to ask her what school she's from, but DEFINITELY not in a mean way like what happened to Lana's friend. I just like meeting new people from new chapters. And I think if she's wearing her letters, and there's no chapter here... she would probably just LOVE for someone to ask her about them. Give her a little chance to reminisce