She was 5-feet-4, 108 pounds, beautifully gaunt and vulnerable-looking. Perfect to be burned at the stake.

And from the moment Otto Preminger picked 17-year-old Jean Seberg from among 18,000 young women desperate to be Saint Joan, she burned (as a Cinderella star) and was burned (by critics and by the hot, pressured atmosphere of public life).

Her first two movies, "Saint Joan" in 1957 and "Bonjour Tristesse" in 1958, were attacked by the critics in reviews that Pete Hamill once said were "some of the worst that any actress ever received." It was said that she was no actress, but merely a celebrity, a soda-fountain girl who was lucky.

Scathed, and some said demoralized, she left the United States for Paris to try a new career there. She had some success-- with "Breathless" and "Lilith"-- and better reviews. She married a Frenchman, returning to Marshalltown, Iowa, for the wedding. In picture spreads in Life and the Saturday Evening Post she was Cinderella again.

But somehow the first fire was gone. Her roles were never what she had hoped. Several marriages withered. Friends said she began to drink and to use drugs more. Life, and her own fears and sensitivities, were setting her up-- setting her up, according to her former husband, Romain Gary, for the FBI to strike the last match, to burn down what was left.

What had been a reasonably good career for an actress, and a difficult life for someone who had hoped for more, now fell into the macabre.

It happened that Jean Seberg had taken an interest in civil rights in America, and that she had contributed to the Black Panther Party. By coincidence, she was pregnant by her husband, the novelist and diplomat Romain Gary. It was one of the years of political distress in America. Richard Nixon had been elected, and the FBI had begun intelligence assaults on those they felt supported the wrong side.

Troubled Jean Seberg became a "target" to be "neutralized." The bureau spread a rumor, which was picked up in the national press, that Seberg would give birth to a child fathered by a well-known Black Panther leader.

The gossip campaign was too much. When she read the story in a news magazine, she became very nervous and soon went into premature labor. She was rushed to the hospital, where she delivered a dead child-- a girl-- who was white.

She was by now so stricken that she carried the dead infant home to Marshalltown. The little body was put in a glass coffin, for all to see her cold, pale color.

Last week, Jean Seberg was found dead in the back seat of her white Renault; on each anniversay of her baby's stillbirth she had tried to kill herself, and this time she succeeded.

In Paris, after the funeral, Romain Gary praised the post-Watergate FBI for admitting it was the bureau that had started the brutal rumor.

"I salute with deep respect that American feat of democracy," he said in a telephone interview. He also lauded America for having delivered fairly and spontaneously the FBI documents to Seberg herself.

"That was about two years ago," Gary said, "and the most amazing, most admirable thing is that she didn't know she could ask for them. What happened is that a vice consul came from the American embassy and delivered an envelope-- and there they were, the FBI documents."

His voice occasionally breaking with emotion, he added: "No American journalist attended my press conference. Only French. When I showed them the documents, they were suspicious. They thought it was a creation of a writer's sick mind. At the end of the conference, a journalist asked me: 'Are you sure they are not fake?' I must say, I lost my temper."

He added, "I owe it to the post-Watergate FBI, if they had not issued a confirmation, to this day I would have been considered a mythomaniac."

Gary (who spoke in English) said that holding that press conference was taking quite a risk, given the fact that a film made from one of his books, "Clair de Femme," had just been released. "It would have been too easy to conclude I was a cheap publicity ,unter," he said.

"But," he added, "I owed it to Jean. She had asked me that if anything happened to her (she thought she might be killed), I was to produce those documents. Besides, my son asked for it, too. Now, I'm bloody happy I did it. I am at peace with myself because I did manage to set the record straight and her image will, forever, remain very pure.

"The whole situation was difficult," Gary said."I never in my life met a more typical American idealist. She was torn between the desire that this thing be known and at the same time, she didn't want to appear anti-American.You know about the American dream and where she came from, it was very strong.

"I, too, was in a difficult position.Being a friend of America, I didn't want to go around with papers exposing the FBI."

Gary claims that Seberg was destroyed by the FBI. "I give you my word of honor that before that, she never had a single breakdown. She wasn't drinking either. She was neurotic. But after that, she became paranoid."

"Remember, I was with her nine years, because we lived together three years before being married. After we divorced, I split my apartment in two so that she could be close to our son." They shared a duplex, of which their son Diego, now 16, occupied the lower part.

According to friends, Gary did more than that. He also kept a close eye on her and made sure her basic financial needs were taken care of.

Gary recalled that when Seberg entered a Geneva hospital (where she had her miscarriage) he spent 10 days with her.

"She really broke down. Everybody who came in had to be searched for weapons. She had a special guard to stay in her room day and night. She was sure the CIA was after her. She really became paranoid.

"When she flew home to Iowa with her dead baby, a little girl named Nina Gary, because under French law, although we were separating, I was considered the father, she broke down on the plane. She came out of the first-class toilets, stark naked and screaming. She was sure the plane was being hijacked. Her bodyguard had to take over, calm her, get her dressed and everybody pretended nothing had happened.

"Already," Gary commented, "the idea of flying home to Iowa to show that the baby was white, that was sick. But she was absolutely in despair that nobody believed that her crusading for the blacks was done in good heart. Worse still, nobody was interested. It's not as if she had an immense international statute."

Gary also emphasized that the reason why he separated from Seberg was because "as I said in a book, 'White Dog,' which is the story of her crusade, I couldn't cope with all that idealism. I felt, I knew, that she was the prey of deadbeats and crooks. She was being exploited. She gave every penny she had. One day, somebody asked for a few thousand dollars for a truck, supposedly for some black charity. The next day, I saw that man driving a two-seat Alfa Romeo."

After her initial breakdown, Seberg remained in fragile condition and was always in and out of psychiatric hospitals. She became cyclic, with long periods of lucidity. According to a friend, who wouldn't be identified, "She was lucid when she committed suicide. I knew her handwriting. The note she left to her son was perfectly controlled."