Health and Human Services Secretary Kathleen Sebelius testifies on Capitol Hill in Washington, Thursday, April 10, 2014, before the Senate Finance Committee hearing on the HHS Department's fiscal Year 2015 budget. Sebelius said 7.5 million Americans have now signed up for health coverage under President Barack Obama's health care law. That's a 400,000 increase from the 7.1 million that Obama announced last week at the end of the law's open enrollment period. The figure exceeded expectations, a surprise election-year success for the law after a disastrous roll-out. (AP Photo/Susan Walsh) AP Photo/Susan Walsh

Health and Human Services Secretary Kathleen Sebelius testifies on Capitol Hill in Washington, Thursday, April 10, 2014 (AP)

Health and Human Services Secretary Kathleen Sebelius has resigned from the Obama administration, a move that comes just months after Americans started signing up for health insurance coverage under Obamacare.

President Barack Obama accepted her resignation earlier this week and will nominate the Office of Management and Budget’s Sylvia Matthews Burwell, 48, as the next head of the HHS, the New York Times reported.

“The president wants to make sure we have a proven manager and relentless implementer in the job over there, which is why he is going to nominate Sylvia,” said White House chief of staff Denis McDonough, according to the Times.

As one of the longest-serving members of Obama’s cabinet, with nearly five years under her belt, Sebelius, 65, was one of the chief architects of the Affordable Care Act, helping to pass the law through Congress in 2010 and contributing to its various mandates.

However, after the disastrous launch of the healthcare.gov website in October 2013, Sebelius’ relationship with the Obama White House reportedly became strained as top administration officials scrambled for answers to what quickly became a national embarrassment. Joined by a handful of aides, Obama blamed HHS for supposedly failing to provide his cabinet with better information on the status of the website’s health prior to its launch.

But the president ignored repeated and increasingly loud calls for Sebelius’ firing and instead tapped Office of Management and Budget director Jeffrey Zients to get the website in halfway working order.

Many of the site’s glitches were eventually worked out, but not before Sebelius began to shrink from the public eye. Recall that when the president took a “victory lap” in the Rose Garden earlier this month and announced that roughly 7.1 million Americans had signed up for health insurance through the online exchanges, Sebelius was not present at his side.

McDonough said Sebelius approached the president last month to discuss her future in his administration.

“What was clear is that she thought that it was time to transition the leadership to somebody else,” he said. “She’s made clear in other comments publicly that she recognizes that she takes a lot of the incoming. She does hope — all of us hope — that we can get beyond the partisan sniping.”

The White House maintains that Sebelius’ sudden departure was her choice and that she was not forced out.

Although she weathered months of questions and criticism from both her employer and critics over the disastrous implementation of the Affordable Care Act, she said she hopes her exit will ignite a new era of bipartisan cooperation in the nation’s capital.

“If I could take something along with me,” she said, according to the Times, it would be “all the animosity. If that could just leave with me, and we could get to a new chapter, that would be terrific.”

But Sebelius’ departure will likely set the stage for a series of contentious confirmation hearings for Burwell as Republicans and Democrats continue to battle over the controversial health care law going into the fall midterm elections.

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This post has been updated.