(CNN) President Donald Trump's nominee to be the ambassador to Singapore could be derailed in the Senate amid questions about whether she properly disclosed to Congress her communications with former national security adviser Michael Flynn , according to senators and sources from both parties.

Lawmakers and senior aides told CNN that they expect the Senate to send her nomination back to the White House when this year's session wraps up at week's end, making her prospects for confirmation increasingly grim. At that point, the White House will have to decide whether to renominate her to the post amid questions over her interactions with Flynn about Russia, and then convince skeptical senators to take up the nomination during the 2018 midterm election year.

If her nomination is derailed, as some senior senators and aides expect, it would mark the second time that Mueller's probe has effectively thwarted a Trump nominee -- the other being Sam Clovis , who withdrew from consideration for a senior Agriculture Department post in November amid questions about his communications with Trump campaign foreign policy adviser George Papadopoulos, who pleaded guilty to lying to authorities about his conversations over Russia

Senate Foreign Relations Chairman Bob Corker, whose committee oversees the McFarland nomination, told CNN that the White House "will have to make decisions on whether they renominate" her to the position since the Senate plans to send her nomination back to the White House this week.

"Nominees that have other productive lives they can lead probably have to assess themselves whether it makes a lot of sense to continue on because it does put your life on hold," Corker said. "Before any of these other things came out, there were significant Democratic objections to this nominee -- the nominee is aware of that. This obviously makes it more difficult."

Sen. Ben Cardin, the top Democrat on the Senate Foreign Relations Committee, wants her nomination sent back to the White House at year's end, according to Cardin spokesman Sean Bartlett. She has not clarified her testimony with the committee, Bartlett said.

To win confirmation this week before the year-end recess, McFarland will need cooperation from Senate Democrats to expedite a vote. But Democratic officials say that's not going to happen.

"No chance she gets confirmed by year's end," said a Senate Democratic leadership aide, adding the nomination will "likely" be sent back to the White House.

The controversy over her nomination reignited this month after unsealed court documents showed that Flynn spoke to a senior transition team official about what to discuss with then-Russian ambassador Sergey Kislyak after the Obama administration issued new sanctions against Russia on December 29 of last year. While McFarland was not mentioned in the court filings, sources confirmed that she was the transition official who spoke to Flynn. Moreover, a New York Times report revealed that McFarland mentioned Flynn's communications with the Russian ambassador in a separate email on December 29.

But in her testimony on Capitol Hill earlier this year, McFarland did not disclose those conversations, despite being asked directly in written correspondence with Sen. Cory Booker, a Democrat from New Jersey.

"Did you ever discuss any of General Flynn's contacts with Russian Ambassador Sergey Kislyak directly with General Flynn?" Booker wrote to McFarland in July.

McFarland responded, "I am not aware of any of the issues or events as described above."

A McFarland representative did not respond to multiple inquiries seeking comment about her plans. The White House also did not comment.

Sources on the Foreign Relations Committee said that they have not received any clarification regarding her testimony.

McFarland's nomination was approved by the panel in September, but it has not been considered by the full Senate. In order to prevent the nomination from being sent back to the White House, the two sides would have to reach a unanimous agreement -- something that is highly unlikely given the controversy her nomination has spawned.