Answer:
Industrial-organizational psychology
Step-by-step explanation:
Industrial-organizational psychology is the field of psychology that studies the behavior of the people at work.
The industrial psychology studies help the students to study the behavior which could help them in selecting the best people for the company, motivating the employees, improving the working skills and many other attributes related to the work and the behavior.
In the given question, since the student works as a cafe and helps the coworkers by motivating them therefore she must study the industrial-organizational psychology.
Thus, Industrial-organizational psychology is correct.