I will admit, this is very much a construction made on-the-fly, without regard to grounding it in any prior works of similar nature. The idea is simple: construct the span of universes that contain a person at a particular point in time. Each universe has some ever-so-slight change in some random quantity of the universe, assuming that there's no random action acting within human consciousness (that is, human thought is deterministic; if it isn't, this whole exercise is meaningless because it implies that they're inherently unpredictable due to random action upon the decision model). Over a sufficiently long enough period of time, the decisions made by that person will diverge exponentially, though not necessarily immediately. It doesn't imply that they're an irrational actor; rather, it implies that the slightest perturbation of circumstance will cause exponentially-increasing errors in any approximation over long enough periods of time. In the end, those universes will cover every single possibility of decisions that can be done by that person.
This, of course, is applying to an identical person acting to slightly different situations with the starting point being the same for each test. Human decision making is chaotic in a second sense as well; the experiences and knowledge feeding into the decision function are themselves chaotic. That is, any slight perturbation of experience or knowledge when applied to the person's decision function will cause exponentially greater distance between future decisions despite being in identical situations.
If I have a person A, and at time t0 have them experience either events a or b, then at time t, the distance between the decisions made following event a or following event b is exponentially related to the distance between events a and b themselves. Note that the orientation of the initial events matters, and can further change the distance between two future states.
In this sense, a sufficiently intelligent AI could predict, given an event, how a person would make decisions further down the road as a consequence of this event. However, assuming that the simulation is relying on an approximation of the experience and knowledge feeding into the human decision function, the exact details of the event, or both, then the simulation will exponentially diverge from reality.