Well personally, I'd give (almost) anything to be the lowly sucker that Keira demands a chair from.
Other than that, I think stars like her almost have a reason to be bitchy when putting up with asshole paparazzi and stuff like that. And to label Keira difficult just because she couldn't quite get a scene right is a bit rough.
For after all what is man in nature?
A nothing in relation to infinity, all in relation to nothing, a central point between nothing and all, and infinitely far from understanding either.