"Culinary staff" would be whatever the person who wrote the announcement wanted it to be. It isn't exactly a technical term.
And it is entirely possible that whoever works in whatever they might have for a kitchen will indeed all be women that one night during that one screening. How many people are we talking about, do you think? Two? Three? Four?
Possibly even every night. Who knows? Do you? Can you contradict the claim with anything even vaguely resembling evidence, or even likelihood?
Some people are trying waaayyyy too hard to work up anything they can to be poutraged about.
It looks like the most parsimonious explanation is that there isn't anything there worthy of even a little, teeny, tiny poutrage.
Sorry to disappoint.