Shirley MacLaine is talking about co-star Meryl Streep, trying to describe what the celebrated actress is like offscreen. “Listen,” MacLaine finally says, “I’m not sure I even met Meryl. … She probably comes to work as the character so I don’t know what she’s like. She’s telling people she was intimidated by me, but that’s her character talking. How can you be intimidated when you’re Meryl Streep?” Not even director Mike Nichols, who has helmed three of Streep’s films, including the new “Postcards From the Edge,” knows where her characters end and she begins. “I’ve caught her again and again trying out her characters in life,” says Nichols. “One time, she gave me a passionate kiss when she arrived on the set in the morning. It took me until lunch to figure out what she was doing. Meryl would never do that. That was her character. … While we were making `Silkwood,’ I saw `Sophie’s Choice,’ and I was deeply shocked. I thought we had the real Meryl but it turns out they had just as real a Meryl.”

Streep, who has donned many disguises – wigs, accents, period costumes – laughs at the notion that the “real Meryl” is something of an enigma. “I don’t think I’m that remote or unknowable and neither does anyone who I’m related to or close to,” she says. “The real me? How could I let the real me into Lindy Chamberlain (`Cry in the Dark’)? She’d talk like somebody from New Jersey. That’s stupid. I can’t do that. I go where the roles are. I probably wasn’t all that successful at making myself really like Isak Dinesen (`Out of Africa’) but parts of me are very much in that character.” According to Streep, there’s even more of the “real Meryl” in Suzanne Vale, the woman she plays in “Postcards From the Edge,” the Nichols comedy co-starring MacLaine, which opened in Lehigh Valley theaters on Friday. “This is closer to the vernacular me than anything I’ve been offered in a long time.”

In the film, which is based on Carrie Fisher’s semi-autobiographical novel, Streep plays Suzanne, a drug-addicted actress who is forced to move back home with her movie-star mom (MacLaine) after suffering a near-fatal overdose. Streep says she related to Suzanne’s “parade of insecurities. I have insecurities about my singing and my looks. There’s a certain cynicism that she has and a sense of humor. It’s not Lindy Chamberlain. It’s not Isak Dinesen. It’s not Sophie Zawistowska. It’s me more than any of those have been.” Streep’s first introduction to Hollywood movie-making came in 1977 when she landed an itty-bitty role opposite Jane Fonda in “Julia.” Playing a sarcastic debutante, Streep stole her scene with a flick of her mink stole. Since then, she’s not only stolen scenes, but whole movies and, some say, the mantle of best living actress.

Thirteen years after her film debut, Streep has risen to the top ranks of her profession, earning six Academy Award nominations and two Oscars (for “Kramer vs. Kramer” and “Sophie’s Choice.”) Still, some critics, most notably Pauline Kael and Andrew Sarris, have complained that Streep’s characterizations lack spontaneity. “She’s tried too many accents on us,” chided Kael in her negative review of “Out of Africa.” But Streep may have the last laugh. Witness her decision to tackle a trilogy of comedies, beginning with last year’s “She-Devil” and continuing with “Postcards From the Edge” and the upcoming “Defending Your Life” opposite Albert Brooks. Streep denies she has a specific game plan in mind. “I go where I think the writing is best or where I think there’s an issue or a particular passion that I can understand, that relates to me. It’s a matter of whether the woman on the page calls to me. If she does, then I have to go there.”

“Postcards” marks the first time Streep has sung in the movies except for her duet with Jack Nicholson in “Heartburn” and her renditions of “He’s Me Pal” in “Ironweed” and “Amazing Grace” in `Silkwood.” “I have a fear of singing in front of people,’ says the 41-year-old actress. “And here was a character who had the same fear. My mother used to say to me, `What are you agonizing for, you have a beautiful voice. Just sing it!’ But the more she would say that, the more I couldn’t. And I would undermine myself with my nerves. I would self-destruct. In the movie, when Shirley said to me, `Go ahead, go ahead and sing,’ I was 12 again. It all washed over me – that horrible, watery feeling.” Streep’s greatest asset as an actress is her ability to physicalize her characters’ emotional states with the smallest of gestures. Think of Streep’s swagger as Silkwood and the way a simple flip of her long, blond hair communicated the severity of her character in “Manhattan.” Offscreen, she’s just as animated, raking her fingers through the air to make a point, frowning when she hears a question she doesn’t like. Streep hates being interviewed – a fact she feels compelled to share. “This experience makes me feel like a piece of meat,” she says when asked if she ever feels exploited by the film business.

She’s good-humored, but ill-at-ease. Even sitting down, she’s all nervous energy. She runs her hands almost incessantly through her hair, which is newly cropped. (“I don’t have time to do my hair in the morning,” she says of her short do. “I got sick of it being an issue.”) Streep can’t (or won’t) detail how she manages to transfigure the static words of a script into a flesh-and-blood character. “I don’t know what it is I do,” says the Yale-trained actress. “I’m not analytical. I don’t work with a method so I always feel kind of terrified at the first step.” “Goldie Hawn gave me a clue about Meryl,” notes MacLaine. “She said, `She’s not really acting, she’s channeling.’ I think Meryl’s probably transcended what the rest of us do.” Streep giggles when she hears MacLaine’s and Hawn’s compliments. “Oh those girls,” she smiles whimsically. Nichols gushes: “All the movies I’ve done with Meryl, there’s always a pattern. She arrives at rehearsals and two days later the leading man is in love with her; the woman who plays her best friend is indeed her best friend and the guy who’s the villain is afraid of her. He stays out of her way. Meryl sort of re-arranges her soul to accomplish these relationships. She gets it right, and then all the other actors have to do is show up.”

Streep’s dedication to her craft is legendary. She has gained weight – 30 pounds, in fact – to play Lindy Chamberlain in “Cry in the Dark” and razored her hair for “Sophie’s Choice.” The later film is one of the actress’s personal favorites. “When I was making it, I remember telling my husband that I thought nothing would ever touch this experience. I was depressed when it wrapped, and then two weeks later I went to Texas and made `Silkwood.’ And that was, in a different way, as satisfying. I liked playing her, and I’m very proud of that performance.” One of the reasons “Postcards” was attractive to Streep was that it presented an accurate examination of the ways Hollywood chews up and spits out actresses. “It’s like a docudrama,” she says.

Has Streep ever felt victimized by the Hollywood power structure? “Yes, of course,” she says. “When I went up for `Out of Africa,’ I heard a rumor that Sydney Pollack didn’t think I was sexy enough for the part. So I got a padded bra and a low-cut dress for my first meeting, and I got the part. Now, I’m sure it was my Danish accent and my intelligence and ability to portray a writer. It also probably had something to do with the cleavage. It’s so depressing.” Despite rumors of a hot-and-heavy liaison with frequent co-star Nicholson, Streep has remained married to sculptor Don Gummer for 12 years. The couple and their three children live most of the year in Connecticut. The rest of the time they reside in a recently purchased $3 million Spanish-style house in Los Angeles. “`Postcards’ is my first Hollywood movie,” says Streep, who’ll next co-star with Nicholson in the Bob Rafelson-directed “Man Trouble.” “I’d never been on a sound stage in my life.”

Speaking of Hollywood, Streep is angry about what she calls “the crash and burn” of “Evita,” the long-anticipated film version of the Andrew Lloyd Webber play in which she was set to star. She’s angrier still at reports that she dropped out of the project because she was suffering from exhaustion. “Basically, it fell apart for financial reasons. I wasn’t tired. I mean I’m tired all the time, it’s not like that just came over me because of the negotiations. I wasn’t exhausted, I was insulted. It’s a big, long horrible story. ” One bright spot for Streep: From the wreckage of “Evita” rose “Postcards.” “I had been preparing for over a year and a half to do `Evita,'” she says. “But I was just so happy Mike and Carrie wanted me for this part. I like smart talk. I’m sort of verbal and I loved having something to chew on for once that was funny, witty. I wish Carrie could write my interviews.”

“Postcards From the Edge.” Rated R. Now playing at Eric Allentown 5 and Eric Easton 6.