Papadopoulos' fiancee, Simona Mangiante, told CNN in an interview that Papadopoulos was "everything but a coffee boy" who worked with senior members of the Trump campaign.
Mangiante said she is speaking out now because her fiance cannot.
"His contributions to the campaign has been much more relevant than bringing coffee," she said. "I think they wanted to disassociate from the first person who decided to actively cooperate with the government, on the right side. And probably the easiest way out is to dismiss his personality and lower him to a low-level volunteer."
Papadopoulos' role on the Trump campaign has been the subject of intense debate since his guilty plea was made public by special counsel Robert Mueller in October. The court documents detailed how he reached out to a London professor with connections to the Russian government who had offered damaging information on Hillary Clinton.
"Few people knew the young, low level volunteer named George, who has already proven to be a liar," Trump tweeted the day after the guilty plea was made public.
"It was a volunteer position," said White House press secretary Sarah Sanders. "And again, no activity was ever done in an official capacity on behalf of the campaign in that regard."
"He was the coffee boy," former Trump campaign adviser Michael Caputo told CNN.
But Mangiante, an Italian national, says her fiancee -- whom she first connected with in September 2016 -- was in touch with many high-level campaign officials during the campaign, and he worked with former Trump national security adviser Michael Flynn during the transition. Papadopoulos is pictured in a March 2016 photo of then-candidate Trump meeting with his foreign policy team.
"He worked with Michael Flynn during the transition, and he was actively contributing to the foreign policy strategies for the campaign," Mangiante said. "He didn't take any initiative on his own without campaign approval."
She said he had communications with campaign manager Corey Lewandowski, campaign executive director Michael Glassner, campaign co-chairman Sam Clovis, campaign chairman Paul Manafort, executive chairman Steve Bannon, campaign adviser Rick Dearborn, and, during the transition, Flynn. Most have denied, downplayed or said they didn't recall their interactions with him.
"He helped those editing Trump's speech on foreign policy. He attended many events and entertained contacts with high level officials of different countries," Mangiante said. "He was actively giving his input and insight in terms of strategies, and of course he was in contact with high level officials and got approved for any initiative."
Papadopoulos also represented the Trump campaign at various meetings
with foreign officials up to Inauguration Day. He met with a British government official, and the Jerusalem Post obtained video
showing he met with Israeli settlers in Washington.
Mangiante said that Russia was a secondary issue for Papadopoulos on the campaign, and his work focused more on Egypt and Israel.
As a foreign policy adviser, Papadopoulos made numerous attempts to connect the Trump campaign with senior officials in the Russian government.
Court documents show Papadopoulos emailed campaign officials
in March 2016 about setting up a meeting in Moscow "between us (the Trump campaign) and the Russian leadership to discuss US-Russia ties under President Trump."
A campaign supervisor, who was not named in the court documents but is now identified as Clovis, responded by saying "great work."
"I would encourage you" to "make the trip, if it is feasible," he later wrote.
Mangiante said the campaign's deputy communications director, Bryan Lanza, who is now a CNN contributor, signed off on Papadopoulos doing an interview with the Russian news agency Interfax. Lanza declined to comment.
Mangiante said that Papadopoulos did not talk about his Russia connections with her, but she was interviewed by the FBI in October.
A key focus of the interview, she said, was on the professor who met with Papadopoulos and offered the dirt on Clinton, who has been identified as Joseph Mifsud.
Mangiante said she hopes Trump will pardon her fiance, who is awaiting sentencing and continues to cooperate with the FBI.
"I'm very proud of it, of this choice to cooperate with the right side of history," she said.
This story has been updated.