She's always supported the public option. People keep writing articles acting like this is a new thing, but it has been true since the 2008 campaign and even as far back as HillaryCare in the 1990s.
Did she? I don't recall the public option being a feature of either Obama's or Hillary's healthcare plans in 2008, although the latter was more aggressive in that it included a universal mandate (which is ultimately what became Obamacare) whereas Obama's initial plan only included a mandate for children. The 90s plan also featured employer mandates instead of a government plan. If anything, the public option is a fairly new aspect of Democratic healthcare proposals.