This IS a LONG shot indeed!
How do you know she isn't related to you, and more importantly what research have you done already?
I am not of your continent but in the UK at that time there was a trade journal called the Drapers' Record. Is /or was there something similar in US? If this fashion model was employed for many photoshoots with different companies she may feature in such a trade journal.
With a bit more information from you, some message board reader with related fashion interests may be able to assist.