A debutante, or not?

Last week's New York Times obituary of Ted Kennedy described his first wife this way:

That same year (1958), Mr. Kennedy married Virginia Joan Bennett, a debutante from Bronxville, a New York suburb where the Kennedys had once lived.

Whenever I see debutante, the context seems to suggest a rich woman. But I've never looked it up, and when I did this time, I found it has a very specific meaning. It may have been misused in this Ted Kennedy obit and definitely has been misused other times I have seen it.

The American Heritage Dictionary definition is "A young woman making a formal debut into society." Bennett was 22 in 1958, and if she did make a formal entrance into society, I'd assume it would be at a younger age than that. And I know I've seen debutante used to describe married women, which would be wrong.

However, I could be wrong about 22 being too old to be a debutante. Formal entrances into society are a tradition with aristocratic origins (presenting young Ladies at court, etc.), but I have no idea in what form those traditions continue among the U.S. upper class. I did find a NYT article from last year about modern debutante balls in New York ($14,000 a table), and all the debutantes in that story were 18. Can anyone shed some more light on the issue?

The AHD gives this etymology for debutante: "French débutante, feminine present participle of débuter, meaning to begin."