I received an email this morning from Greg King, author of FOTR:
The bit about Marie flinging herself against the storeroom doors and pounding on them, trying to get them open, was from Kudrin's 1963 statement. So only the storeroom door at the end of the room. And he says as soon as this was noticed Ermakov shot her - probably the wound in the thigh (given that I'm still absolutely convinced that the skeleton exhumed in 1991 was Marie's, not Anastasia's, who was only found ten years back), as he aimed beneath the smoke. And Marie slumped to the floor (though hadn't yet suffered any fatal wounds).
I hope that helps clarify!
So Marie did try to escape the murder room and was shot in the leg, likely by Ermakov, according to Michael Medvedv-Kudrin. This is not corroborated by any of the other killers. Also, the killers had little interaction with the grand duchesses while they were alive, so I am skeptical of the specific identification.