According to the Huffington Post, in March 2014 Clinton said, "she supports Obamacare, and opposes single-payer health insurance."
According to a February 2014 report titled, The Hillary Papers, Diane Blair, a political science professor and friend of Clinton's, "wrote that Hillary Clinton vouched for a single payer health-care system during a family dinner in 1993."
During the 2008 presidential campaign, Clinton introduced a healthcare plan that would mandate insurance coverage for all Americans either through a private insurance plan or employer-provided insurance. She proposed funding the program by repealing the Bush tax cuts. According to Newsweek, "It was Obama who ultimately came around to Clinton's point of view when he included the mandate in his own health care proposal."
In a 2004 op-ed, Clinton wrote, "As Senator John Kerry has proposed, we should cover everyone living in poverty, and all children; allow people to buy into the federal employee health benefits program; and also help employers by reinsuring high-cost claims while assuming more of the costs from hard-pressed state and local governments."
Hillary Clinton was a chief proponent of the Bill Clinton's Health Security Act, which proposed "to reform the health care system so that all Americans are guaranteed comprehensive health coverage."
Clinton was instrumental in the passage of the State Children's Health Insurance Program, which provides matching funds to states to provide health insurance to children in low-income families.
As I keep saying, she supports whatever the polls tell her to support.