As a former P.I., it shouldnt be that hard to locate her. But it will take some time and effort. But then again, thats what makes it fun and all the more fullfilling when you do locate her.
-You have her name, the year she graduated and the school name. If you havent already, join and then look/post with classmates.com.
-Start with the school under that name closest to where you found the ring (Tenn. to Ohio is not that big of a stretch) and call them. Emails get lost or passed over or simply ignored. Asked the office secretary if such and such person was in the class of '04.
-Look on the various school websites and see if they have a contact for a PTO person and try to contact the
historian. They would be the one who would have documented the students and are most likely to know them by name.
-Do a name search on
http://zabasearch.com/ and see if you have a name in the city/area as one of the schools (if she was 18 when she graduated she probably had not changed her last name from that of her father's).
-Check around on MySpace.com and see if you find anything.
If you want, email or pm me her name and what you have, if anything. I have no interest in the ring but if I can find anything out for you, I'd be happy to pass it back to you and you can make the contact. ( I enjoy doing this sort of thing)
Best of Luck and Kudo's for looking.