(CNN) The former adviser to first lady Melania Trump, who has come under fire for the cost of President Donald Trump's inauguration, was among the event planners who raised concerns about excessive spending in the weeks before the events, according to documents obtained by CNN.

Stephanie Winston Wolkoff, a former friend of Melania Trump, has emerged as a witness for investigators and received a subpoena last month by Washington DC's attorney general.

The 10-page subpoena, which has been seen by CNN, asks Wolkoff to hand over a variety of information, including any evidence of inaugural-related expenditures that were "wasteful, mismanaged, and/or improperly provided private benefit."

It asks for communications between the inaugural committee and several business entities connected to President Trump or his family, as well as communications between Wolkoff and a number of Trump family members, including Donald Trump Jr., Eric Trump, Ivanka Trump and Jared Kushner.

Multiple agencies are investigating Trump's inauguration, including federal prosecutors in New York who are scrutinizing tens of thousands of documents handed over by the Presidential Inaugural Committeeaccording to people familiar with the inquiry . Authorities are investigating whether any of the donation money was misspent, used to improperly benefit certain individuals or came from foreign donors. Vanity Fair first reported the DC subpoena.

The DC subpoena is the third Wolkoff has received about the inaugural's finances. The other two were from the US Attorney's office in New York's Southern District and from the House Oversight Committee, according to a source familiar with the matter.

Reached by CNN, Wolkoff said she could not comment, citing a nondisclosure agreement she signed with the 58th Presidential Inaugural Committee, the nonprofit group that oversaw Trump's inauguration.

In a one-page statement released in April 2019, Wolkoff said, "If the PIC were to release me from this obligation, I would be able to speak freely without the fear of legal or financial repercussions. Otherwise I am regrettably unable to provide any substantive comment."

But two people close to Wolkoff tell CNN that she has responded to the latest subpoena. That could be worrisome for people connected to the inauguration.

Wolkoff was deeply involved in minute details of the inauguration planning and was included in emails viewed by CNN that included costs, schedules and vendors, among other information.

One of the sources close to Wolkoff told CNN that she is meticulous about record-keeping, and has maintained extensive records of her work surrounding the inauguration, including detailed ledgers and spreadsheets of budget expenses.

Welcome to Washington

This is a story, essentially, of a clash of wills and culture. Wolkoff came to Washington unversed in politics but expert in staging large-scale productions for high-end, notoriously detail-oriented cultural institutions, such as the Lincoln Center and Vogue magazine. She was used to working with people she knew and trusted and expected that her role would include checking the price of every line item, according to the sources. She was told she would be given carte blanche, they say. That turned out not to be case.

Stephanie Winston Wolkoff and Melania Trump in 2008.

Wolkoff left the White House in February 2018 amid controversy , when it was revealed that her firm, WIS Media Partners, was paid close to $26 million to plan events for the inauguration.

That month, senior administration officials said the President and first lady were not pleased to have learned about the money paid to Wolkoff's firm by the Inaugural Committee, according to The New York Times

now the White House press secretary, The first lady's former spokesperson Stephanie Grisham,now the White House press secretary, released a statement at the time saying the White House had "severed the gratuitous services contract with Ms. Wolkoff."

In her April 2019 statement, Wolkoff disputed that she had been fired, and wrote that Grisham's words were "not fair or accurate," and that she had been "thrown under the bus."

All but $1.6 million of the $26 million payment to Wolkoff's company went to vendors and subcontractors for broadcast production services of events, according to a document prepared by the company and viewed by CNN.

The Inaugural Committee was chaired by President Trump's longtime friend, the California-based financier Tom Barrack. The committee's deputy chairman, Rick Gates, became an employee of Colony Capital, Barrack's investment firm, after the inauguration.

In February 2018, Gates pleaded guilty to conspiracy and for lying to investigators, on charges unrelated to the inauguration. Gates is currently cooperating with various investigations, as part of his plea agreement.

Barrack has come under scrutiny recently over his dealings with Saudi Arabia.

Asked about the recent subpoena to Wolkoff, spokespeople for Kushner, Gates, Barrack, Donald Trump Jr. and Eric Trump all declined to comment.

The White House would not comment but has previously said the President and first lady were not involved in inauguration planning.

Double the cost

The Trump Inaugural was different in many ways, most notably in what it cost. The event's record $107 million price tag was more than twice as expensive as President Barack Obama's 2009 inauguration, as well as the 2001 swearing-in of President George W. Bush.

Wolkoff, a longtime friend of the first lady, was asked by Ivanka Trump to run the inauguration after the election, according to one of the sources close to Wolkoff. Wolkoff had a reputation as a strong event planner, having run the Metropolitan Museum of Art's Costume Institute Gala, known as the Met Gala, in New York City.

Once she landed in Washington, Wolkoff realized that the scope of the inauguration was far beyond what had been outlined to by her Barrack and Gates, according to one of the sources. She'd have to trust the "Washington way," which included, so she was told, working with long-held partnerships.

Thomas Barrack

Four sources familiar with the situation tell CNN that Wolkoff clashed repeatedly with Barrack and Gates over the Inaugural Committee's spending. A particular point of contention was a vendor called Hargrove Inc., a special events company that Wolkoff felt was charging prices beyond what she thought was reasonable. Hargrove has been involved in producing events for every presidential inauguration since 1949 and was paid at least $25 million for Trump's inauguration.

Emails obtained by CNN show the concern Wolkoff and other event planners had about Hargrove's budget. In late December, Gates was copied on an email exchange between Wolkoff and Hargrove managers that said, "I am expressing my concerns because I have no options at this point." Wolkoff cited "many line items that were not reflected, rentals that were not sourced, budgets that were not accurate and décor elements that were not feasible."

Hargrove's then-president replied that "our only goal here is to make this the most successful inauguration ever," and offered to provide 10 bars free of charge.

An email among inaugural event planners also questioned Hargrove's prices, with one saying a bid to decorate two halls of the convention center was "literally 5 times anywhere else would be. We've accounted for some premium increase, but this is exceptionally high."

Another email from another partner in the event planning asked Hargrove why the price was so high for scenic elements, writing that the "cost ... is not justified with how it has been explained or shown." CNN did not see Hargrove's response to this email.

Despite the concerns, Gates approved the hiring of Hargrove for Barrack's Chairman's Global Dinner held at Andrew W. Mellon Auditorium, one of multiple events the company was involved in, and the Presidential Inaugural Committee signed off on Hargrove's budget, according to documents viewed by CNN.

Hargrove declined to comment for this story, but a source familiar with the company's work on the inaugural events said Hargrove submitted a detailed scope of work documents and invoices and because the scope of work changes with each inauguration, any comparison with other events would be unfair. Hargrove produces many other major events, including the Democratic National Convention, and CNN has, along with other media outlets, worked with Hargrove in its convention coverage.

A spokesperson for Gates told CNN he had no knowledge of Wolkoff's concerns over Hargrove. Barrack's spokesperson refused to comment, though it is unclear whether he knew about the cost concerns.

Rick Gates

Wolkoff soon felt excluded from meetings convened by Barrack and Gates that she thought she should have been included in, according to one of the sources close to her.

Things got so bad that Wolkoff voiced her distress in a phone call to Trump's then-personal attorney, Michael Cohen, who recorded the call. According to a source with knowledge of the recording, Wolkoff told Cohen that she was concerned about the inaugural spending.

The recorded conversation was acquired by federal agents last year during their investigation into Cohen.

Wolkoff, according to the two sources close to her, had gone to work for the Inaugural Committee against the wishes of the majority of her New York friends, many of whom supported Hillary Clinton.

Wolkoff has told one of those sources, a close friend, that she took the job because she felt she had no choice due to her close relationship with the first lady, as well as a sense of patriotic duty

Despite the friction surrounding the inauguration, Wolkoff agreed to work for Melania Trump as an unpaid adviser. Classified as a special government employee, Wolkoff spent a lot of time working from New York City. She was tasked with crafting certain messaging points, as well as cultivating the first lady's official children's initiative , though to what extent remains unclear. Wolkoff departed the first lady's staff in February 2018 -- Be Best was launched in April.

Privately, Wolkoff has told multiple people that it's her belief she was deliberately set up as a scapegoat to deflect attention from other people involved with the inaugural who, to her mind, were guilty of misspending and with whom she grew to have a difficult relationship.

"Stephanie was underestimated," says a person close to Wolkoff. "They were hoping for a New York socialite who would not look at the details."