Now, look for an image similiar to the sister from Allston's Two Sisters and/or Hunt's Lost Profile.
You might discover other images, because there are many "what the thing is not" images in this painting. Right now only look for the lady profile. Once you see it, you should not have any doubt. It is not photographic, but the shape, the profile, the head, neck, and shoulders are very well defined.
The next slide has the lost profile image marked.