There is a great collage out there comprised of side by side photo's of the Romanov's & era then and now. This photo is one of them beside a picture of those same steps today-the contrast is striking...and haunting.
This is Alix, the girls appear to be Tatiana to her right, I want to say Olga on the left, which would make me think the third would be Maria...but it looks like it might be Anastasia.