THE 1980 MEDIA STAR award for Most Promising Newcomer has got to go to Mary Cunningham of Southfield, Mich., who discovered at the age of 17 that she couldn't be a priest and went to Harvard Business School instead. She was a terrific hit there, and after she graduated, she was swamped with offers that started at a cool $50K a year. Lots of corporate recruiters came courting, but in the end it was Bill Agee of Bendix who won her mind. The rest, as they say, is history, and in the end, Mary Cunningham had to resign from her job amid rumors that her "rocket to success" was fueled by something other than talent. The story captured America's heart and Mary Cunningham ended up starring in a newspaper series by Gail Sheehy.

That series, put together last Thursday night and distributed by the Chicago Tribune-New York News syndicate, was picked up by newspapers all across the country."I don't think I've ever seen anything move like this has," says Pete Willett of the syndicate. And readers from Boston to Miami and Washington to Los Angeles who had never heard of the Bendix Corporation were transported into a real-life corporate drama of the first order. Eat your hearts out, Harold Robbins, Jacqueline Susann, Sidney Sheldon. This one's for real. This story comes complete with jets, intrigue, high stakes, brillant people -- one beautiful woman.

"a real raving beauty," was the way Willett put it.

Mary Cunningham is nothing if not beautiful, and after all the pop psychology gets written and the corporate soul-searching about women in the boardroom gets done, the bottom line on this saga will still be that the Mary Cunningham story would never have happened if she had looked like Lily Tomlin.

Looks never hurt, we are told. It is better to be pretty than to be plain.

Maybe that's true most of the time. I, for example, have never heard of a man being described as too good looking unless he was being cast for a movie role. Certainly Mary Cunningham fits the image of the good-looking corporate executive, but by being a young woman, she didn't fit all of it.

And she wasn't just pretty. She was beautiful. Whatever the relationship is or was that she has or had with William Agee, her looks surely sharpened the daggers of others. No 29-year-old is going to come into the 88th largest industrial corporation in America and become vice president for corporate acquisitions in a mere 15 months without arousing jealousy. There is a great tendency to find sexism in the Mary Cunningham story. But there is also a need to sort out the various realities in it, and one of those realities is that a 29-year-old man on the kind of fast track she was put on would probably have to contend with a lot of the jealously she faced. What made her situation different is not just that she was a woman, but that she was a beautiful one. That opened the way for the corporate attacks on her to take the form of sexual innuendo. People believed she was having an affair with Agee, not because she was constantly with him, but because she was beautiful. None of this would have happened had she been a man. But none of it would have happened had she been ugly.

One of the ongoing discussions generated by the women's movement has to do with a woman's looks, and whether an attractive woman should capitalize on her looks or mute them in an effort to dispel sex-object images. The question that comes up in these discussions is: Will a beautiful woman be taken seriously or will her looks diminish the value of her mind? Mary Cunningham, quite obviously, did not subscribe to the school of thought that would have had her pulling her blonde hair back in a bun and popping a set of horned-rimmed glasses on her nose.

Early on in this saga, right after Agee told a meeting of 600 Bendix employees that Mary Cunningham was being promoted strictly because of her talent, she told reporters that the world wasn't ready for someone like her. She phrased it more gracefully, but what she was saying was that America wasn't ready to believe that there could be a beautiful 29-year-old woman who could be so smart that she could do what Cunningham did on the basis of talent alone.

She is right, of course, which is what makes her story fascinating and why we want to know how she got the way she is, and why newspaper editors across the country have paid money to print everything they can get their hands on about her, and why her picture is becoming as familiar as Farrah Fawcett's. Whether Mary Cunningham and William Agee were having an affair of the heart doesn't really matter anymore. They were certainly having an affair of the mind.

She has become a larger-than-life character, the star of a newspaper soap opera, a victim perhaps of her ambitions, and certainly of her looks. She has gone from Bendix to notoriety, which is not something that corporations look for on job applications. If she's looking for work, well, it's a good thing she has a master's degree from Harvard Business School.

For Mary Cunningham, looks are not something to fall back on.