I don't know the connection between these Edwardian ladies, but suspect it might be a shared interest or place of worship. The hinge on the door looks like it could be to a church door or communal building of some kind and those may be some kind of benches that you can see just on the right edge. If not connected through a church or chapel, they could be teachers (the younger girls teaching assistants) and the building a school. The lady in the black dress has a very masculine appearance when you look closely. The postcard doesn't give any clues, not even a photographer's name or location.