As the Mighty Mighty Bosstones sang, "I'm not a coward, I've just never been tested."

Moral luck (based on your summary; haven't read Nagel) isn't much different than other kinds. Someone born into money can never demonstrate they have the power to pull themselves up from the bottom, someone with a loving family can never show they can overcome the same adversity as an orphan, etc.

There's a good question, though, of whether morality is thought- or action-based. Is Norma immoral, or if she found herself with an opportunity to cheat, would she be forced to confront what might have been a fantasy up to that point and reevaluate it as a moral question?

(I suspect the answer's different for different Normas, of course.)