Kirstjen Nielsen is out as President Trump’s Secretary of Homeland Security. She’d long been a target of Trump’s criticism. He pressured Nielsen to be more agressive at stopping migrants from illegally crossing the border, and to severely limit the number of asylum-seekers to the U.S. Nielsen joined the administration as John Kelly’s protégé when he led the Department of Homeland Security. When he moved to White House Chief of Staff, she took over his old job. “Mr. President, thank you for the honor of this nomination and for your extraordinary leadership.” But Trump quickly grew frustrated with Nielsen. Last May, she told colleagues she was close to resigning after Trump berated her in front of the entire cabinet for what he said was a “failure to adequately secure the nation’s borders.” She pushed back, however, when pressed about it. Reporter: “Could you tell us what your relationship is with the president, and if those reports about a resignation letter are in fact true?” “We have a very strong relationship. I think what is true is we’re both really frustrated.” The president also questioned her loyalty given her previous work in the George W. Bush administration. Nielsen may most be remembered for carrying out the administration’s “zero-tolerance” policy at the southern border, which resulted in the separation of thousands of migrant families. “Here is the bottom line: D.H.S. is no longer ignoring the law. As long as illegal entry remains a criminal offense, D.H.S. will not look the other way.” But the policy became a lightning rod. “It’s a shame and a disgrace.” “The fact that children are being torn out of the arms of their mothers is on Donald Trump’s head.” “It is inconsistent with our American values to separate these children from their parents.” Trump eventually signed an executive order ending the policy. “We’re keeping families together, and this will solve that problem.” Ultimately, Trump felt she never did a good enough job on immigration and border security. With Trump increasingly dissatisfied that his hard-line immigration policies weren’t being implemented properly, her dismissal may have been inevitable.