WASHINGTON (-) — The former U.S. ambassador to Ukraine was removed from her post after insisting that Rudy Giuliani’s requests to Ukrainian officials for investigations be relayed through official channels, according to a former diplomat who has spoken with her.The ambassador, Marie Yovanovitch, is scheduled to testify before congressional lawmakers on Friday as part of the House impeachment inquiry into President Donald Trump. Democrats say they expect her to appear despite the White House’s position that no administration officials cooperate with the probe.Yovanovitch was recalled from Kyiv in May as Giuliani — who is Trump’s personal attorney and has no official role in the U.S. government — pushed Ukrainian officials to investigate baseless corruption allegations against the Bidens.In a July 25 call, Trump told Ukrainian President Volodymyr Zelenskiy that Yovanovitch was “bad news,” according to a partial transcript released by the White House.Neither Giuliani nor Trump have specified their objections. But a former diplomat, recalling a recent conversation with Yovanovich, said she was removed after insisting that a request for Ukrainian officials to join in an investigation be relayed according to long-established protocol.The former diplomat said Yovanovitch refused to do “all this offline, personal, informal stuff” and made clear that the U.S. government had formal ways to request foreign governments’ help with investigations.The former diplomat insisted on anonymity to disclose the private conversation.The State Department traditionally relies on mutual legal assistance treaties, under which U.S. and foreign officials agree to exchange evidence and information in criminal investigations.Yovanovitch is scheduled to speak to the House Intelligence, Foreign Affairs and Oversight and Reform committees behind closed doors Friday as part of the impeachment investigation. Despite Trump’s assertion that his administration will not cooperate, three people familiar with the deposition said that Yovanovitch is expected to appear. The people requested anonymity to discuss the closed-door meeting.On Thursday, 10 Democratic senators sent a letter to Secretary of State Mike Pompeo demanding an explanation for Yovanovitch’s removal before the end of her three-year assignment.“In particular, her early recall raises questions about whether you put the personal interests of the President above the Department’s career personnel or U.S. foreign policy,” they wrote.Earlier this week, the White House sent Congress a letter outlining its opposition to the impeachment probe and refusing to cooperate with requests for information, including interviews with administration officials. The House committees have moved to subpoena officials instead.Even before the testimony, the attention on Yovanovitch was renewed Thursday after U.S. prosecutors arrested two Florida businessmen tied to Giuliani, charging them with campaign finance violations. An indictment filed in the case alleged that the men, who were raising campaign funds for a U.S. congressman, asked him for help in removing Yovanovitch, at least partly at the request of Ukrainian government officials.Yovanovitch has led U.S. embassies in Kyrgyzstan and Armenia and is now a State Department fellow at Georgetown University. The director of the Georgetown program, Barbara Bodine, said the former envoy is declining all requests for interviews.Former colleagues of Yovanovich said Trump allies’ characterizations of her as politically motivated are off-base.She is “a top-notch diplomat, careful, meticulous, whip smart,” and unlikely to have badmouthed Trump, either to Ukrainian officials or her colleagues, said John Herbst, a predecessor as ambassador in Ukraine who worked alongside Yovanovitch there in the early 2000s.Yovanovitch has always known that the role of diplomat “wasn’t about her” but about “serving American national interests and supporting the people around her,” said Nancy McEldowney, a former U.S. ambassador to Bulgaria who now directs a Foreign Service program at Georgetown.___Associated Press Writer Jocelyn Noveck contributed to this report.