Natascia Diaz plays Anita in Signature Theatre's revival of “West Side Story.” (Eli Meir Kaplan/For The Washington Post)

And then there was the time Natascia Diaz danced for Jerome Robbins.

She was still a kid, only a few years out of Carnegie Mellon’s drama program. But she had already toured Europe in a production of “West Side Story,” playing Anita, a role she would return to over and over — and has returned to yet again, at Signature Theatre in Arlington.

Robbins was at New York City Ballet at the time, readying “West Side Story Suite,” an excerpt from the musical that included Anita’s signature number, “America,” and he was in need of a ballet understudy. It was the mid-1990s, and it just so happened that Diaz was auditioning for a new American tour of “West Side Story” that required Robbins’s casting approval. And that’s how she came to be standing in a rehearsal studio in Lincoln Center with “West Side Story’s” legendarily intimidating maestro choreographer.

“So let’s do ‘America,’ ” Robbins said to her.

The young actress did as she was commanded. “I sang and danced everything,” she recalls, “just me and the pianist and him there.” Which is even more fraught than it sounds: “America” is the show’s most explosive production number, and she had to generate all that exuberance on her own. As she shouted the final word of the song — “Olé!” — “I fell flat on the floor. And he was laughing.”

Actress Natascia Diaz, who is playing Anita in Signature Theatre's revival of "West Side Story," rehearses a scenes with Sean Ewing as Bernado. (Eli Meir Kaplan/For The Washington Post)

Diaz remembers it not as terrifying but as exhilarating. “Don’t work so hard!” Robbins commented as he left the studio. And although she won the Anita under­study job (and even went on in the ballet, one time), she didn’t exactly take the choreographer’s advice to heart. For if there is one essential thing you glean about Diaz, it’s that she is eternally working soooo hard.

“Natascia gives you everything,” says Matthew Gardiner, director of Signature’s “West Side Story,” the company’s first crack at a show that turns up on most lists of the greatest musicals of all time. “She is a perfectionist to the point that can be maddening. But it’s never in a vain way. It’s always in service of the story. She gives more to a production than I’ve ever seen anybody give.”

Schooled in ballet as well as drama, Diaz was a regular presence on New York stages a decade and a half ago, singing and dancing in a series of high-profile Broadway and off-Broadway musicals. Her path, she says, “was in my DNA”: Her Puerto Rican-born father, Justino Diaz, is an opera singer; her Italian-born mother, Anna Aragno, is a psychoanalyst who started as a ballerina. Those early-career original New York musicals in which she was cast struggled for critical and audience acceptance: Paul Simon’s “The Capeman” in 1998; Paul Scott Goodman’s “Bright Lights, Big City” in 1999; Lynn Ahrens and Stephen Flaherty’s “Seussical” in 2000. All had interesting aspects but none caught fire. And then, suddenly, a new avenue opened up for Diaz, 250 miles south of Manhattan. She was hired to play Petra, the earthy servant who sings “The Miller’s Son” in “A Little Night Music,” one of the six musicals revived in the Kennedy Center’s well-received Sondheim Celebration during the spring and summer of 2002.

That engagement exposed Diaz’s vivacity and sensuous energy to a new city, and the city embraced it. If you’re any kind of regular theatergoer in Washington, you no doubt have seen her in one eye- and ear-catching performance or another. Whether at an institution as large as the Kennedy Center, where she was in “Carnival,” in 2007, or as intimate as MetroStage in Alexandria (2008’s “Rooms”), she’s become a routinely imported member of greater Washington’s company of distinguished players.

“It’s not like I said, ‘I’m going to D.C. — screw New York,’ ” Diaz remarks as she unwinds during a break in rehearsals at Signature. “My agent’s in New York. My mom’s in New York. I haven’t left it.” She still, in fact, lives most of the time in New York. And yet she’s discovered a special level of work-life satisfaction here — as well as a beau, whom she doesn’t want to name.

“Everything I’ve found myself doing here in D.C. runs the gamut of color and texture, from plays to musicals,” she says. “It happened so organically.”

Though there have been forays into the classics, as in the “Measure for Measure” she was a part of at Shakespeare Theatre Company in 2013, musical theater, and Signature, have been a crucial local anchor. Gardiner, Signature’s associate artistic director, says he reminded Signature artistic chief Eric Schaeffer of Diaz’s work in “Carnival” when Schaeffer was looking for an Aurora, the sultry screen siren, for his 2008 revival of John Kander and Fred Ebb’s “Kiss of the Spider Woman.”

Schooled in ballet as well as drama, Diaz was a regular presence on New York stages, singing and dancing in a series of Broadway and off-Broadway musicals. Her path, she says, “was in my DNA.” (Eli Meir Kaplan/For The Washington Post)

Schaeffer, who curated the Sondheim Celebration, knew and liked her work, so Gardiner revved up his lobbying campaign. “I remember texting Eric, saying ‘I know who your Spider Woman is, it’s Natascia Diaz.’ I’d even leave around head shots of her for him.”

The “Spider Woman” experience drew Diaz into an elite circle at Signature, to which she returned in 2014 for one of her most memorable Washington-area turns, as Pirate Jenny in Gardiner’s revival of the Brecht-Weill “The Threepenny Opera.” It was the sort of part in which Diaz excels: an impassioned survivor whose voice emerges from somewhere bruisingly, soulfully deep.

She’s a galvanizing stage presence, the type of performer a spectator’s eye naturally gravitates to. Perhaps that is why Anita, the fiercely loyal girlfriend of the Sharks’ leader, Bernardo, remains one of her touchstone roles. It’s the part that made an Oscar-winning star of Rita Moreno, the Anita of the 1961 movie version, and has been a career high-water mark for generations of actresses on Broadway, from the role’s originator, Chita Rivera, to Debbie Allen, to Karen Olivo, who won a Tony playing her in the 2009 revival directed by the musical’s book writer, the late Arthur Laurents.

To Diaz, Anita is surefire because of the care and precision Laurents, composer Leonard Bernstein and lyricist Stephen Sondheim took with the character. “Her arc is perfection,” the actress says of the way Anita is propelled from feisty, sexy queen bee to scarred, grief-stricken victim. “The writing is so sparse and elegant. Everything is structured with her so that it’s the most bang for the buck.”

It’s a measure of how compellingly Anita is written that Diaz has never felt she was done with the part. In one long stretch in the late ’90s, she played Anita on tour for more than a year, a period over which the rhythms of the portrayal became so ingrained that “to this day, they’re tattooed to me.”

Not that it was by any means effortless. “The cycle was, I’d be flying high, getting all my laughs, feeling strong and confident,” she says. “And then one night, I would lose a laugh, or a moment felt forced, and it would get to a point where I felt, ‘I don’t know what I’m doing anymore.’ Then I would begin to rediscover it. I would give myself notes: ‘I need to have more surprise there,’ and I would work on it. And soon, I would find myself up and floating again. And every time I would go around that circle, the cycle of discovery and recovery got deeper and deeper and deeper.”

To have a character swimming around in your system for 20 years might sound constricting. But maybe when you’re encouraged by a musical-theater innovator of the caliber of Jerome Robbins, you never really get a character out of your system.

“I never had a problem being inspired,” Diaz says. “The minute you put on this music, it goes right to my soul.”

West Side Story Music by Leonard Bernstein, lyrics by Stephen Sondheim, book by Arthur Laurents. Directed by Matthew Gardiner. Tickets: $40-$111. Through Jan. 24 at Signature Theatre, 4200 Campbell Ave., Arlington. Visit sigtheatre.org or call 703-820-9771.

Correction: A previous version of this report misspelled Natascia Diaz’s first name in one reference and gave an incorrect location of where her mother was born.