When three teen-age girls, Pam Shriver among them, reached the semifinals of the Dallas women's pro tennis tournament in March, Bellie Jean King said, "Some day we will look back at that as a landmark tournament."

Sam Shriver remembers it, too.

He is Pam's father, an insurance executive from the Baltimore suburb of Lutherville. So when his 15-year-old daughter defeated two of the world's top 10 players to reach the Dallas semis, he and his wife, Margot, caught the next plane to Texas.

Pam didn't like that.

She lost in the semis to Evonne Goclagong, throwing away a 5-2 lead in the first set.

"Part of her problem that day," Sam Shriver said yesterday at a happier moment, "was that we showed up. It upset her that we were there. Like, you know. "This is my show, what are you doing here?"

If Dallas comes to be remembered as the landmark that thrust onto center stage the successors to Evert and Navratilova and Goolagong, the Shrivers will remember it more as a difficult time for a teen-ager full of herself.

Tomorrow, Pam Shriver can win the United States Open women's championship. Yesterday's 7-6, 7-6 victory over the No. 1 seed, Martina Navratilova, was important for that, but Sam Shriver found another reason to like it.

His little girl is growing up.

"The difference in Pam from Dallas to now is that this time she invited her mother to come see her play," Shriver said. Margot Shriver couldn't make it yesterday, but she will be here tomorrow.

"Win or lose, Pam's had a good tournament," her father said.

Throughout yesterday's match, the crowd at the National Tennis Center gave its vocal support to Pam Shriver, even to the extent of cheering a costly doubt fault by Navratilova. Now 16, tall and trim, Shriver has a faultless baby face that invites affection. It was hers yesterday.

But had the paying customers spent time with Shriver after that Dallas performance, they might have held back a smidgen of their outright doting.

For two or three months, Pam Shriver was, her father said, your basic wise-guy teen-ager who knows everything and wonders why the world is so very, very dumb.

"You have children?" Sam Shriver asked a reporter. "Then you know how they can be at 15, 16. She was fighting everything. That's how teen-agers are. Fighting herself, your parents, school, discipline - whatever restraints there are in a teen-ager's life, she was fighting them."

Pam Shriver's coach, Don Candy, noticed that most of all. He was with her for a three-tournament tour of England. First time out, she lost in the first round to an anonymity named Marjorie Blackwood. Then Lea Antonopolis, an American of no special note, dispatched Shriver in a second round match.

At Wimbledon, on Center Court, Shriver reached the third round and led Sue Barker, 6-2, 5-2, and had three match points. From that narrow jumping-off spot to glorious victory, Shriver leaped to ignominious defeat, 2-6, 8-6, 7-5.

"Center Court has her by the throat," Candy said at the time. Shriver choked, he was saying, and as proof that time passes and teen-agers grow up, she yesterday spoke of that match as if it were decades ago, not 10 weeks ago.

"I didn't choke any of those points away today," she said. "I like I did in the Barker match."

Candy was please this time.

"Ever since Dallas, her attitude has been lousy," the coach said. "I'm saying this constructively, and I just hope she lives through what has happened here.

"After Dallas, after beating the No. 7 and No. 8 players in the world, she couldn't believe anybody could return her serve. 'They hit my serve back,' she said."

Here, Candy took on a pouting look in imitation of his prodigy's terrible suffering.

"She was saying. 'I don't like grass courts." ' ' ' 'I don't like wind' . . . "Where is she on the computer? . . . She was all tangled up in the wind.

"So I had to say to her. 'What the hell is this, Pam? They've got a racket, too.'

"It was a joke."

Shriver yesterday said Candy gave her a stern lecture after the England trip and she has been working very hard since. The victory over Navratilova was her biggest ever, and in the first moments after Navratilova hit a backhand long at the end, everyone expected Shriver to celebrate extravagantly.

She simply shook Martin's hand and smiled a lot.

"I didn't want to make a big scene, to jump up and down," Shriver said. "I thought of Martina, for some reason, I didn't want to rub it in."

Pam Shriver is 16 and getting older every day.