Indeed! I think yours may be from the days before she became an actress, like a promo head shot used as she looked for work. It looks like she is in her late teens. She was nominated for an Oscar at age 20 or so.
Check out these photos of her in her 20's. Looks very much like your photo, but more "Hollywood" glammed up:
You made me giggle, don't you just hate it when you get so excited about something and then on closer inspection you're all bummed because maybe it wasn't what you thought it was. You're a doll, thanks so much for your feedback on the oldies, it's always interesting.