This confuses me more....
OK let's see what we have...
So the picture may be 1912-1914 (?)
Maria turn her hair at age 15 in 1914 and as you said their last cruise on Standart was 1914 ( But where did they go i couldn't understand) I hope it wasn't Finland because there will be no chance to understand is it Olga or Maria...
But Sarushka look.... There was a trip to Finland 1915

This is what it says in livadia.org...
"Olya and I near the beach at Peterhof, on the Gulf of Finland, 1915. "It's kind of strange because
"beach at Peterhof" ?!?! and
"on the Gulf of Finland"There are mistakes in the site... because i saw in Olga's pictures one formal of her in court dress where she is with her hair down and next to it another one from her formals where she is with her hair up (there was a session and Tatiana was with hair up there too ) And so this could be again mistake