"The ball girls don't have their T-shirts," said one sleek woman to another.

"They don't?"

"No, and it's 1:51."

"Well, we start at 2. What are we going to do?"

"I thought you'd be able to tell me."

Welcome to the $100,000 Virginia Slims of Washington women's tennis tournament. It opened yesterday at George Washington University's Smith Center with everything in place but those darned old T-shirts.

Snooty-looking silver cars bearing the sponsoring cigarette company's logo clogged the arena's driveway, giving hope to the elitists who think tennis is still their province. A horde of men in blazers walked around kissing all the tennis players they hadn't seen since March. And a woman in a russet-colored dress dragged out her binoculars, not to watch the action but to scan the crowd.

If the woman had looked at the 1977 inaugural of the Slims tour, she would have seen Bethesda's Nancy Ornstein try to match muscle with Mariana Simionescu and come away a 6-3, 6-3 loser. There is a chance the woman with the binoculars heard about Ornstein's loss. It was accompanied by cries of agony from section 107.

"Sorry about the kid yelling," the 24-year-old Ornstein told Simionescu afterward. "That was my brother, Stevie. He's 13 and he gets a little carried away. We had a big lecture before we left the house, but it didn't do much good."

Simionescu, 20, Romanian refugee who is engaged to Bjorn Borg, was in too good a mood to let a little noise ruffle her.

This was her first match in three months and she was trying to alter her big-hitting style. "I used to knock the ball over the fence," she said. "Now I'm trying to keep it on the court."

She succeeded marvelously. Ninety-eight per cent of her old power was there along with the dandy drop shot she has always had and the lethal backhand she has been refining in months away from the tour.

Simionescu won't have much of a chance to rest her newly developed weapon. She will be back on the court today against Greer Stevens of South Africa, trying to stay alive in a field that couldn't be tougher if there were mines planted in it.

Simionescu will be playing in the 11 a.m. session, which will showcase No. 6-seeded Mima Jausovec and No. 7 Francoise Durr. Admirers of Chris Evert will have to wait until the 5:30 p.m. half of the tennis double-header to see Miss Moneybags of 1976.

"It's twice as good as it used to be," said Simionescu after using her backhand to finish off Ornstein.

Beth Norton, a judge's daughter from Fairfield, Conn., won $675 last year, approximately $108,050 less than Evert. But she got some hope for the future yesterday, coming back to beat Ann Kiyomura, 3-6, 6-3, 6-1.

Kiyomura, who was half of the championship women's double team at Wimbledon in 1975, stayed ahead of Norton early, but never by much.

That was what convinced the 19-year-old Norton that if she put her mind to it, she could avoid an early exit.

"I told myself I had to stop making errors," said Norton. "I haven't played in a tournament since Forest Hills and I had butterflies. I wasn't watching the ball. I had to start getting my first serve in and I has to start making my passing shots better. Once I did that, it was simple."

Norton waited until Kiyomura was ahead, 3-1, in the second set before she made it look that way. Nobody could have been more stunned by the turnabout than Kiyomura, who lost nine straight games before she rallied briefly.

When Norton wasn't foiling her with a drop shot or a lob, Kiyomura was undoing herself by slamming the ball into the net.

"Oh, Annie," she cried in frustration, but even that failed to rouse her.

Sen. Floyd Haskell (D., Colo.) knew where of Kiyomura spoke. He was study in desperation as he teamed with Val Ziegenuss to go down in flames, 6-2, in a celebrity doubles match with Wendy Overton and Sen. Lowell Weicher (R., Conn.).

But Weicker, who rammed one scoring shot into Haskell's gently spreading middle, didn't put much stock in what he accomplished.

"Unfortunately," he said, "the Republicans win all the sporting events and the Democrats win all the elections."