Personally ... I don't believe Beverly Oliver was in the plaza. I've listened to her talk about the assassination several times and the story she spouts doesn't sound like it comes from a first-hand witness. She gives me the impression of someone saying what she's heard happened. She was supposedly witness to something horrific ... considering the proximity she'd have been at. But she just comes across as someone trying to make a living from the story she might have gatecrashed.
Going by the company she was keeping - RD Mathews, Jack Ruby, Joseph Campisi, etc, wouldn't really be too hard to imagine she's just another chancer - like those lot.
Although, saying I don't believe she was there ... I was reading through an old thread about Jack Lawrence, and it was brought up by a researcher that Beverly Oliver claimed to have been dancing with JL at the Egyptian Lounge on the night before the assassination. She knew Ruby, RD, her old man was a mobster crook. What if she was really there, in the plaza, that she was filming the assassination knowing the big bucks a film of the event would give her/them. Kinda interesting theory.
Maybe the real Babushka lady was someone B. Oliver had heard was there for just that reason. Just in case the film ever turned up - she decided to fill the starring role.