I've never had a problem with them not eating or drinking but then I really don't baby them either. I figure this is nature's way of producing more offspring and nature isn't going to create a situation where the mother dies of starvation or dehydration prior to hatch so….I make sure she has water and food she can access and leave it up to her to eat and drink. I think a lot of people worry their bird isn't eating and drinking because they don't see it. They only take a short break once or sometimes twice in a 24-hour period, so unless you are there ALL the time, it would be easy to miss it.
Its not so much "mean" but protective of their eggs - and you want that.