Answer:
overjustification
Step-by-step explanation:
Overjustification: In social psychology, the term "overjustification" is described as a phenomenon in which an individual's play activities becomes a work in order to get rewards or payment. In other words, it is considered as a process through which an individual's intrinsic interest related to a few activities or behaviors is being replaced via the presentation of some "external reward".
In the question above, Stella’s change in her views about singing is due to overjustification.