I think the key is knowing what high school she went to. From there, you could possibly get yearbook pictures and student lists. Knowing an approximate age would narrow the possibilities significantly as well.
There are no digital yearbooks from the high school. I checked
And then scrolling thru all the friends lists of all their friends on Facebook.
(Especially if they have nicely sorted their friends into "High School" friends.)
Twitter lets you do the same thing.
I've seen entire classes all "Friend" and "Follow" each other.