First, congrats on getting your first choice - AChiO! And you told your story very well.
Second, ZTA is big in the south (has the most chapters in SC out of all the NPC orgs) but not as big as others in other regions, so I'm not surprised if she hadn't heard of it if your school isn't in the south like where the rest of your family went (and I know firsthand how you can't hide Zeta pride) BUT, I remember looking up the NPC website as a NM and finding out about the other orgs we didn't have at my school. I wanted to know all about sorority life, not just my specific org! So really, asking if it's a real sorority is just, well, ignorant.
Congrats again, and thanks for feeding the GC love of recruitment stories until we get our fix next month when spring recruitment begins! And thanks for not trying to do it in real time - we appreciate it