Meg, how could you? Taking dictation from J.R. Ewing is bad enough, but taking him to bed? When you husband was out of town! Posing with nothing but a double sheet!

What would the nuns say?

"They LOVE it," says Gallagher, better known as Louella, J.r.'s secretary on the CBS smash hit "Dallas." "They watch me every Friday night."

Was it that long ago we were sneaking Marlboros in your bedroom? Or swimming in the 12-and-under freestyle or playing field hockey or writing love notes to Jimmy Tract whom I had a crush on but who -- like every other boy within three suburban counties and at least two states -- liked you better?

It's not surprising that you got J.r. eWing. You always got your man. You were the king of girl who could walk into a rec-room party wearing a new pair of short shorts, giggle, and walk out five minutes later, the remains of shattered teen-age romances in your wake. You were Marilyn Monroe and Bambi and Veronica all rolled into one.

Oh Meg, I saw the article in Us magazine. The one that said you're 26 and having an "on again-off again" romance with ABC's "Taxi" star Judd Hirsch. I also saw the tabloids, the headline that screamed "Dallas BEAUTY MEG'S PSYCHIC FLASH LED TO A NEW LOVE" (how you found true love with "Flash Gordon" star Sam Jones after dumping Hirsch. "Sam is gorgeous inside and out. It must have been destiny," you were quoted as saying.).

I saw the headline "DEATHBED SECRET OF JR'S LOVER." The story said you decided to become an actress at 17 after convincing your mother who was dying of breast cancer that she wasn't really dying.

"Aren't the ridiculous ?" Gallagher laughs.

Is Sam Jones really her "heart-throb"?

"We're just good friends," she says.

As for the discrepancy in the years between high school and Hollywood, Gallagher says "Everyone's younger out here."

No matter. You, Meg Gallagher who lived across the street from me on fishers Road in Bryn Mawr, are the first celebrity to blaze forth from our neighborhood since Katharine Hepburn. From Main Line snooty to Dallas sleaze.

"I'm real proud of myself," says Gallagher in a telephone interview from her West Hollywood home. "I've been to bed with J.R. twice. It was FUN. It was GREAT! That's when I have the best time. I bet I made a few people's eyeballs pop back home. They're so straight ."

(A spokesperson for the School of the Holy Child in Rosemont, Pa. -- where Gallagher spent her formative years wearing knee socks and learning how to curtsy -- confirmed that the nuns have a picture of "Louella" on their bulletin board and they do watch "Dallas" every Friday night. Religiously.)

So what's J.R. like in bed?

"STEFFI, DON'T ASK ME THAT," Meg shrieks. Then, back in character, the sultry Louella, the Louella who spys on Bob-bay , who cheats on her husband, says, "Eat your heart out."

"I love the character," Meg says."Louella loves J.R. She's his personal secretary and confidant. He's taught her everything she knows. Her husband's always away. She has womanly needs and wants. She's crazy about him."

Which is exactly how Meg feels about costar Larry Hagman.

"He's a RIOT. I really love him. I can't believe I'm on the show. It's the hottest television show in the world. In the HISTORY of television, even. They know me in Australia ."

She started out like most would-be starlets, the cutest girl in the class. Long, straight brown hair, sapphire-blue eyes, Camay beauty cleanser complexion.The original Heartbreak Kid.

But there was tragedy in her life. Her mother did die of breast cancer when she was 17. Meg, the oldest of 11 children, presided over the brood, which included three more children when her father remarried. Meg left the Philadelphia suburbs two years later for Broadway. We ran into each other a few times at 30th Street station in Philadelphia. I was a college student in Washington and she was pursuing a modeling career in New York. The last time my sister saw her, Meg was passing out perfume samples at Bloomie's.

Gallagher then enrolled at the American Academy of Dramatic Arts and landed a contract as the Close-Up toothpaste girl. She was also seen in a Bayer aspirin commercial, wearing pigtails.

Three years ago, she left New York. "I was dating this guy and he didn't want to get married, and I did. So I packed up and moved to California. I had nothing but my clothes."

She was out of work for three months until fate hit in the form of a fender bender.

"I was driving to some theater to drop off a guitar for someone. I was in a rented car. All of a sudden, this guy pulls out and almost hits me. I got furious. He said, 'You're pretty when you're mad.'"

Nooo!

"Yes! Can you believe it? He said, 'I bet you're an actress.'"

The guy turned out to be the producer for the now-defunct television series "Delvecchio." He gave her a two-line part. She walked on, spoke her lines and fell in love with the show's star, Judd Hirsch.

They've been on again-off again ever since.

"We're not living together, but we're dating," she says. "I'm also dating Sam Brown."

By the way, she says, "What's Barry Goldwater like?"

"Junior or senior?"

"Junior. Is he a playboy?" Meg asks.

"I don't know."

"Well, we've been seeing each other out here for a few years. I always say he's a playboy."

She like the dimple-chinned congressman, she says, because "he tells me what's going on in the world."

Two years ago, Gallagher tried out for a small part on "Dallas."

"They wanted someone to play a fashion coordinator," she says. "I showed up in sneakers, blue jeans and a T-shirt. They had me read these lines just like a fashion person would. They also told me to put some makeup on. Well, afterward I asked them if I could read in my own voice. So I read just like me and they offered me the part of J. R.'s secretary because Tina Louise was leaving."

For the first two seasons, Gallagher's lines were limited to the following: "Mr. Ewing's office," "Good morning, Mr. Ewing" and "Line two, J. R."

Then, when Mary Crosby came on as Kristin, Louella's part was written out. "She went off to get married," says Gallagher.

This season, Louella came back in style.

"I went from having two lines to hopping in the sack with the HOTTEST guy in show business," Gallagher says. "I worked hard for it. I prayed hard for it."

Yes, Meg Gallagher says she still attends Mass once a week. She lives with her younger sister Lizanne and a dog named Busby Berkeley. She says "Dallas" isn't all the glamorous.

"You have to get up at 5 in the morning, schlep over to the studio. You can't go out at night because you have to look good the next day."

She gets paid by the episode and shoots her scenes at MGM studios, not on location. She says she doesn't know what Louella will do next. "They're very secretive about the scripts. They like to surprise their audience." she says.

What would Meg like to do next?

"Comedy," she says. "This is really only a steppingstone."

By the way, she is asked, what ever happened to that football player she was dating, Ed Mara . . .

"Ed Marinara," she shrieks. "He's of 'Laverne and Shirley'!"