Answer:
Self-fulfilling prophesy
Step-by-step explanation:
A self-fulfilling prophecy is a belief of a person about the future. This belief expectation is strong because this belief is held by the person himself. This concept appears regularly in a culture. In this concept, a person has a strong belief and expectation about the future. The placebo effect is a great example of a self-fulfilling prophecy.
Thus in the above question, Sarah's belief is the example of self-fulfilling prophecy.