This is exactly the kind of statement that requires litigation or arbitration, though, because there's no definitive evidence that that's true.
I personally agree with you that the movie probably would have made less money without the Premier Access option, but what we think doesn't really matter. Disney would argue what you said and have facts/figures/experts to back it up, and her team would argue the opposite with their own facts/figures/experts. It would be down to a jury or the arbitrator to decide who's right.
I still say there's a 99% chance it never gets to that point, though, either through settlement or because of a determination that the plain language of the contract already resolved the issue.