In her native Denmark, she’s known as Queen Margrethe III — a wry nod to the considerable power she wielded as government economic minister. Some Danes also call her the Queen of Twitter for her popular social-media feed, which features her reactions to TV talent shows as well as economic policy.

Today, Margrethe Vestager is known as the woman going after Google.

And with that, she has assumed a potentially much larger throne.

Vestager, now Europe’s top antitrust regulator, announced Wednesday that she was formally accusing Google of violating European antitrust laws by favoring its search results over those from competitors. While an investigation of Google had dragged on for five years without result, Vestager’s decision to aggressively target one of the most successful U.S. businesses — a move criticized by President Obama — suddenly kick-starts the European Union’s highest-profile antitrust suit since its lengthy battle with Microsoft a decade ago.

Vestager is the leader and public face of the E.U.’s claim that Google abused its market power to restrict competition. “And this, in my opinion and in our preliminary review, is not as it should be,” she said during a news conference Wednesday. “And that is the reason for this endeavor.”

European Union's competition chief Margrethe Vestager speaks during a media conference regarding Google at EU headquarters in Brussels. (Virginia Mayo/AP)

Shortly after the announcement, she hopped on a plane for Washington, where she will give two speeches on antitrust issues and meet with U.S. regulators before giving two more speeches in New York on Monday — events that should raise her profile even higher.

Those who know Vestager and watched her long climb to her new perch describe her as respected, intelligent and unwilling to yield to political pressures when she believes the facts support her, even when it may hurt her.

“She’s known for being a tough cookie,” said Marlene Wind, a political science professor at the University of Copenhagen.

Vestager, 47, took on the role as the E.U.’s competition commissioner in November. She faced a full plate of potentially controversial ­cases, including ones involving Google, Russian energy company Gazprom and questions about tax evasion in Luxembourg. Her predecessor as antitrust chief, Joaquín Almunia, had tried and failed repeatedly to reach a settlement with Google. To many observers, he appeared hesitant to file a formal “statement of objections” against the company.

Vestager showed no such reservations. She said she viewed the formal accusations as a way of prodding the case toward resolution. Google has 10 weeks to respond in writing. A hearing before E.U. commissioners could follow, along with a formal trial. A settlement could be reached anytime along the way.

“For me, the road from here is open,” Vestager said. “I would like to hear what Google has to say for itself.”

Google issued a statement Wednesday defending its business practices, calling the E.U.’s accusations “wide of the mark.” The company says that consumers have more choices than ever and that other online firms are thriving.

Vestager’s willingness to be confrontational — to challenge Google in public rather than hold more-private discussions — has surprised many people.

“It’s a very un-Danish way of doing things,” Wind said.

That should serve as a warning to the American company.

“Google shouldn’t underestimate her,” Wind added.

Vestager, who holds a master’s in economics, started her career as a civil servant working in the Danish government’s finance ministry. She eventually assumed the roles of the country’s education minister and economic minister.

She’s a longtime member of the Radicals, which, despite its name, is a centrist political party. It’s a small group, garnering about 10 percent of the national vote, but critical for forming coalition governments with both the larger liberal and conservative parties in Denmark. And Vestager has often played influential government roles — to the point that many considered her more powerful than the ruling prime minister.

But she’s not propelled by political calculation, said Kristian Madsen, U.S. correspondent for Politiken, Denmark’s largest newspaper, where he also served as a longtime political pundit.

“She’s data-driven, and in that sense, unideological,” Madsen said.

During her party’s last campaign in 2011, the slogan was “Listen to the economists. That’s what we do.” The very unsexy message was that the emotional pleadings of politicians should not overshadow the facts. As economic minister, Vestager pushed through an overhaul of Denmark’s pension system, raising the retirement age and changing benefits. That wasn’t popular with voters, Madsen said. But Vestager was unperturbed.

“She’s very set when she thinks she’s right — which is most of the time,” Madsen said. “She’s no fan of the negotiating table.”

That could hurt Google, which theoretically could face a $6 billion fine and be forced to change how it does business overseas. Vestager said she is not after Google changing its search algorithm or redesigning its pages. Given the speed of online innovation, she said, she was more interested in an agreement on principles.

“I am very, very open to solutions as long as they address the concerns that we have — that there is conduct that hampers consumer choice and innovation in general,” she said.

The E.U.’s current accusations are focused on its assertion that Google unduly favored its own comparison-shopping tool called Google Shopping over those from competitors. Vestager said the inquiries into other areas — Google Maps and Google Travel, among them — were ongoing. The E.U. also announced that it was opening an investigation into potential anti-competitive practices with Google’s Android mobile operating system.

“So there could be more statements of objections,” Vestager said.

Despite her tough tactics, Vestager is regarded in Denmark as warm and possessing a dry wit. When a new government was formed in 2011, she and other politicians made headlines during the traditional visit to inform the queen, in this case Margrethe II, because they traveled on bicycles. Vestager’s ride had a large wicker basket on the front.

And during Wednesday’s news conference, Vestager made a joke about Google as she answered a reporter’s question. She began by noting how pervasive Google is in Europe, where it has 90 percent of the search market, compared with 67 percent in the United States.

Google has inserted itself even into our language, she said.

“If you look for something, you say, ‘Let me Google it.’ And if you want to say something about what may not be the wisest question — and I’m not alluding to you,” Vestager said, smiling, as laughter rolled out from the audience, “they would say, ‘Let me Google it for you.’ ”

“So it’s in our behavior,” she said. “It’s in the way that we work.”

And, to her, it needed to change.