I didn't read the other responses, save for the first couple, so excuse me if I am repeating what someone else has said.
I don't think she should have made a judgment call by saying being spiritual makes for a good nurse. However, I agree with the first response. Maybe the instructor didn't express her message correctly, or you misinterpreted it.
Here is my opinion: you are not obligated to be spiritual, since it is not necessarily a given quality in all nurses. If you are not personally spiritual, you should not be expected to believe what the patient believes. But, it is beneficial for you to respect the patients' beliefs, and allow the patient to be spiritual. In other words, don't pass judgment on their beliefs, or question them. I think being spiritual helps people cope with things that happen in their lives, and offers some kind of "grand-scheme" meaning to it. Questioning or judging these beliefs would not only be insulting, but harmful. Which would go against, "Above all things, do no harm." At the same time, it is important that you respect the patients' decision to not be spiritual, so you don't push your beliefs onto them. I think it's okay to tell people about what you believe (if they ask), but don't expect them to agree with you or tell them they're wrong if they feel otherwise. Maybe you could learn something from each other?
That may be what she meant.
Edit: I hope this thread doesn't become solely about religion and our opinions about religion, rather than ADDRESSING THE ORIGINAL POSTER'S QUESTION!!