At first, I couldn't find much about her and then I found the below correspondence from the American Consul. Apparently, she left the U.S. in 1911 and, when she tried to return, her citizenship was questioned.
As Edna explains, she went to Alexandria, Egypt, in September 1911 "as a member of the Foreign Mission of the United Presbyterian Church of North America." and "remained with the Mission in Egypt until 1916, when I left and entered upon war work, helping to manage several tea rooms for soldiers in Alexandria and supporting myself."
Her mother wrote a note verifying her birth in the United States and a member of her church provided documentation of her birth, baptism, and membership in Bethel Presbyterian Church.
I then searched Passport Applications and found hers, which included the
picture above. I also found her on a passenger list returning to New
York City from Plymouth, England.