Alice's visions are contingent on the current state of people's decisions. If someone is going to change their mind, but is not certain to do so and hasn't yet, she doesn't necessarily see the future where they do (I'm not sure whether she gets it as one of many possibilities or just doesn't get it at all). This means that Jokers thwart her pretty thoroughly, because Jokers spend most of their time doing things they weren't likely to decide to do and didn't plan very far in advance. ~the power of whimsy~