Okay, there's no need to panic. Just because someone hasn't surfaced as an adult after having made a few TV appearances as a child (and was otherwise not a public figure), that doesn't mean she's dead! Well, it doesn't mean she's not, either.
I did find this (scroll down to entry #52):
http://www.spiritoftheking.com/guestbook/guest-3.html
Now, of course, I have no idea if that's the same person or not, and the odds are probably against it. For one thing, she could likely have a different name now. But there may be any number of possible reasons we haven't heard from her since. Who knows, she may not want the attention. I'm reminded of the story of Harry Spear, one of the kids in the Our Gang films:
http://www.catsafterme.com/blog/archives/2098
Hopefully, she's doing well and happy, wherever she is now! (But hey, the internet is really cool, and if Sesame Workshop asked about the "test pilot Gordon" and found him, I guess anything is possible.)
EDIT: There is a "Josephine Calvan Orozco, '87" listed at the "Honor Roll Of Donors" (under "$5 to $249") at the Berleley College Of Environmental Design website:
http://ced.berkeley.edu/ced/alumni-friends/honor-roll-of-donors/2009-2010/