As long as you remember her last name in school, you should be able to find her. Go to the school, if you still live in the area, or see if a friend has a yearbook with the spelling of her last name.
Then go to www.classmates.com . or go to www.reunion.com. If this person is still alive, she may be a member of these two popular sites to locate old classmates.
If you locate her, its probably a sign she is ok. Send an email through the sites. You may have to join membership for a year.
To get the names of victims, I went to Yahoo.com and typed in the subject "victims of airplanes that hit the World Trade Center" It gave me many web sites to choose from. Most likely if she was from San Francisco, she was in Flight 93. Just check her name on that list