Hi Kristen,
So sorry for the delay in replying! I tested this to see if deleting a THATCamp also deletes the admin user. And the answer is no: it doesn’t. Your user account will still exist, and it will allow you to log in to the main THATCamp site here and to any other THATCamps you’re a member of. So, as you doubtless saw, you go to Tools –> Delete Site and then agree to delete the site permanently, after which it sends the site administrator (you) an email with that language about your site and being gone forever and a link to click. Feel free to click that link.
I did get an error message after clicking the link, but it did nevertheless delete the site (and not the administrator’s user account). Let me know if you have any trouble and I can delete the site manually. I’ll see about maybe changing that language, too.