Trying to date the photograph (no information on the back, of course) I noticed that the sister in the center is wearing a button. I enlarged the scan enough to see that it's a campaign button for Eugene McCarthy, who ran for President in 1968.
The woman with the flowers talking to Sister Magdalen looked familiar. Given the way the sisters are beaming I had a hunch it might be the candidate's wife. I did some image research on the Web and I'm pretty sure it's Abigail McCarthy. If I were going to really go out on a limb here, I'd guess that it was sometime before the June primary.
Prominent Catholics in public life frequently made their way to the Mount when they were in town, so perhaps Mrs. McCarthy had given a talk at the College. Or maybe Sister Magdalen, a respected U.S. history scholar, had attended a campaign event with sisters and students in tow. In any case, I can't close the book quite yet on this mystery photo.