I would like to thank 'Ranma Senshi' for taking the time to reply on my behalf about the portrait of the girl. The description you gave of the picture you have in your September 1970 issue of Seventeen magazine sounded vaguely familiar to me - but I will really only know I guess when I see the picture - hopefully some day soon.
It does sound like it just may be the picture I am looking for and I will keep checking to see where I can find this particular issue. If I could see a scan of the picture then I would know for certain.
Thanks again - I'll keep you posted when I locate this portrait.