I think this is probably your great grandmother because the photo's subject has her hand on a column to steady herself. Props were used in this way in the older photos because one had to stand still for such a long time. That probably would not have been necessary by the time your great grandmother's daughters were that age.

You can check the George Eastman database at http://www.geh.org/gehdata.html to see if the photographer was practicing in New York when your great grandmother was a young girl. This database lists photographers from around the world, but mostly in the U.S., the dates and where they practiced, and other information about the photographer. The database is a Telenet database which is not supported by the VISTA operating system. If you have VISTA, you could try your local library's computer.

Good luck. Judi