She and her co-hosts were discussing the State Department's decision to prevent Gordon Sondland, the US ambassador to the European Union, from testifying during a closed-door session with the House Intelligence Committee.
The impeachment probe is focusing on a whistle-blower's allegations that Trump used USA military aid to secure a promise from Ukraine's president to investigate Biden, a leading candidate for the 2020 Democratic presidential nomination, and his son Hunter, who was on the board of a Ukrainian energy firm.
But "early this morning, the US Department of State directed (him) not to appear today for his scheduled transcribed interview", Sondland's attorney Robert Luskin said in a statement.
He has no choice but to comply.
The whistleblower's complaint and text messages released by another envoy portray U.S. Ambassador Sondland as a potentially important witness in allegations that the Republican president sought to dig up dirt on Democratic rival Joe Biden in Ukraine and other countries in the name of foreign policy. After the call, Sondland assured another diplomat in a text message that there were "no quid pro quo's of any kind" with Ukraine.
Hours later, Schiff, House Foreign Affairs Committee Chairman Eliot Engel, D-N.Y., and House Oversight Committee Chairman Elijah Cummings announced they would subpoena Sondland for both his testimony and documents.
Sondland's attorney said in a statement that his client was "profoundly disappointed" that he wasn't able to talk to the committees. While the Democrats are already in court to force some of that evidence, they are making it clear that they do not intend to wait much longer.
Trump has denied doing anything wrong. Articles of impeachment, including for obstruction, could be drafted by the end of the year. The South Carolina Republican is a top ally of Trump.
In a phone call on July, Mr Trump asked the newly elected Volodymyr Zelensky to vote the USA year's White House election.
President Trump said Mr Sondland would only have been appearing before a "short kangaroo". Giuliani was communicating with Zelenskiy about the investigations that Trump wanted.
Democrats have delivered subpoenas to multiple administration officials, including Secretary of State Mike Pompeo, ordering them to turn over relevant documents.
The messages involving Trump's personal lawyer Rudy Giuliani show them coordinating to pressure Kiev into investigating Biden, as Ukraine sought United States military aid and access. In exchange, the American officials dangled the offer of a Washington meeting between Trump and Zelenskiy.
About Sondland: The ambassador is mentioned in a series of text messages between USA diplomats and a Ukrainian aide.
Democrats view Sondland as a key witness who can help shed light on whether Trump withheld military aid to Ukraine as part of an effort to pressure it to investigate Biden and his son Hunter Biden, who was on the board of a Ukrainian energy firm.
The following month, Sondland was part of a text exchange with Bill Taylor, a senior U.S. diplomat in Ukraine, where Taylor repeatedly raises alarm that aid to Ukraine is being withheld to push for an investigation.
If a majority of House members back impeachment, the matter shifts to a trial in the Senate, now controlled by Republicans.
"And they have done it with enormous efficacy and they've sacrificed immensely, and we've basically just said to them, 'See ya.'" The Turks, she added, "are like the hungry wolf trying to kill the lamb", but "Trump woke up on the wrong side of the bed, it appears", and he made a decision to give Turkey the green light, "which is why, finally, the Republicans in Congress have gotten a pulse today".
Elsewhere in Washington, a federal judge heard arguments Tuesday in a separate case on whether the House has actually undertaken a formal impeachment inquiry despite not having taken a vote and whether the inquiry can be characterized, under the law, as a "judicial proceeding".