The actress in the mystery photo is Gloria Dehaven - who is still with us, BTW.
But that's not who she was held out to be in the email Mrs. Paco received. According to the email, it was Frances Bavier, better known as Aunt Bea from the Andy Griffith Show. This was supposedly a picture of her taken back in the 1930s. After posting the photo yesterday, I started getting a little suspicious and began researching it. Alas, the Aunt Bea connection turned out to be a hoax. And it was the striking contrast between Aunt Bea, young and old, that made the whole thing kind of interesting.
Still, Gloria Dehaven. Rule 5 goodness!