This "photograph" of Frances Rolleston is actually NOT a photo of her. The editor of Frances' letters and other acquaintances believed that Frances closely resembled Gainsborough's painting of Sarah Siddons, a popular actress. We know from Frances' letters that her eyes were blue and that as a young woman her hair was brown, also that she had a Roman, that is, aristocratic, nose. 

I took an image of Gainsborough's painting of Mrs. Siddons and altered it by changing eye and hair color. Thus we have the closest representation of Frances' appearance possible, since sadly, she refused to be photographed.