"But I think it is time for her to realise that no one cares what she wants, because the producers decide everything. The sooner she accepts it, the better."
Having made movies before, I don't doubt that she does know that, but she was caught off-guard. No one told her in advance of the change and she didn't know until she was there watching the film and obviously the song was important to her (which makes sense). She didn't demand they change it back or anything. She was just upset that what happened wasn't what she was told and I'm sure she was sitting there waiting for the scene all excited to see how it turned out. No doubt she was feeling a bit humiliated. That's quite a different thing than her simply trying to have things her way.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian