I haven't seen the movie, so I really can't judge Roberts acting, but I have to challenge the comment about how "You're never really convinced that she believes in Jesus or the mujahideen". If that's the case, then she probably did a good acting job. Most politicians (and their supporters) who claim to be religious really aren't, and there was no question that many people who supported the mujahideen did so only because they were the enemy of the Soviets. So if Roberts character came off as insincere in her beliefs in Jesus and the Afghan rebels, then she was probably doing a good job.

I don't think that her character is a politician, just a socialite.

no, she's not a politician, she's one of their supporters.

You really need to see the movie before you start commenting on it.