Final answer:
Behaviorism is the approach that characterizes the statement.
Step-by-step explanation:
The statement 'You don't know what she thinks, but you know how she acts.' characterizes the approach of behaviorism. Behaviorism focuses on observable behavior rather than internal processes, and it believes that behavior can be influenced and shaped by external factors such as reinforcement and consequences. In this case, although we cannot know someone's thoughts or internal mental processes, we can infer their thoughts or intentions based on their observable actions or behaviors.