How can I appreciate this story with and without committing intentional fallacy?

To answer this question, one must understand what intentional fallacy is. Intentional fallacy is based upon the concept of author intent. When reading, one tries to figure out what message the author is trying to get across to the reader based on the author's background and society at the time of its writing. When one does not commit an intentional fallacy, he or she is depending upon what is called Reader Response Critical Theory (or Reader Response, for short). Under this literary lens, the success of the text depends upon the reader's reaction to the text.
Therefore, in Salman Rushdie's short story "Good Advice is Rarer than Rubies," an intentional fallacy could be committed if a reader thinks only about Rushdie's perspective on arranged marriages and cultural/societal norms and expectations. One could then go on to making assumptions about the author and the meaning of the text based on the author's personal ideologies.
On the other hand, when examining the text using Reader Response, you own personal connection to the story is the most important. Here, with the question your teacher proposed, he or she is asking what spoke to you from the story. This poses a personal response, and responses should differ across those who answer the question. That said, one response which could illustrate where one does not commit intentional fallacy would examine the change in the protagonist (because of Miss Rhana's beauty). This could lead the reader down a path of challenging the idea of beauty in the world. It could also illuminate the idea that beautiful women do not need to work as hard as those who are not seen to be as beautiful.
Another possibility could be the irony depicted in the text. It is ironic that Muhammad Ali tends to take advantage of women who seek out his help. Here, he does not take advantage of Miss Rhana, and she, essentially, refuses his help in the end. Also, he had been participating in illegal activities to help some of the women, but here he does not; yet, Miss Rhana thinks he is acting illegally.
In the end, to keep from committing an intentional fallacy, one must examine the text for what it is—a story crafted to make readers think about what is happening, in the present of the text.