I have never seen/met this lady and so cannot verify anything about her; I'm also very wary of dealing with grievances by naming and shaming online. However if this lady does indeed have a long-established pattern of heavily harassing other people, it's concerning if this documentary is going to portray her in a positive light. If nothing else, it might encourage other people to start trying the same tactics to get tickets and seats.
There's a recent comment enquiring about this on the film's Facebook page (https://www.facebook.com/oneticketfilm); the film's account has responded "Of course we will show both sides of the story. The filmmakers are well aware of the relationship certain New York City theater owners and box office managers have with Ms Cochrane and are doing their best to reflect this in the film." Hopefully that will turn out to be true.
If there are a lot of theatre workers concerned about this, could a high-up representative from each theatre contact the filmmaker and offer to be interviewed or provide a statement? I'm sure it would be delicate to manage; there would be a risk of getting bad publicity if it was spun as "Nasty theatre people hate their own patrons, especially old ladies". Any statement would probably have to be fairly 'soft', emphasising preferred theatre etiquette and so forth rather than descending to name-calling. Maybe representatives from several theatres could tackle this jointly to soften the PR blow and provide credence to one another's statements. But I'm not in the industry so am not sure if this would be wise. In any case, it sounds as though the film is about done already.
By the way, does a Broadway theatre have the right to set a code of conduct (within reason) for anyone who enters it, and to eject anyone who violates that code (again, within reason, eg while also providing a ticket refund upon presentation of proof of purchase)? Somebody who gets a free ticket outside the door could argue "I was never informed of the code", but putting it up on a small-print sign at the door or something could cover that. I'm not sure of the laws around this.