She's a variant of a Hollywood atheist - not literally, since she's Catholic, but in the skeptic sense. She's the type who lives in a world where clearly magical/paranormal things happen regularly and she sees them all the time but refuses to believe that other, similar things could be true later because the writers have a fundamental misunderstanding of skeptics. They don't deny this stuff to be stubborn or difficult, but because they haven't ever seen any convincing evidence to believe otherwise.