First, the obvious: Clinton is mixing apples and oranges by conflating caucus totals with primary totals. Sanders has been winning most of the caucuses to date and Hillary has won most of the primaries. For many reasons caucus vote totals are always suppressed by that specific format compared to voter participation in a primary, starting with the fact that voters must be present at their caucus site at a specific hour rather than having the entire day to make it to their polling place during a primary. We actually have a good case in point of the difference it makes in turn out: Washington State.
For some reason, Washington actually holds both a Democratic caucus and a primary. The caucus comes first and that's where delegates really are won, the primary comes later and is only a "beauty contest". In 2008 Barack Obama won both of them. But even though the 2008 Washington State Primary was essentially meaningless, Obama still collected ten times as many popular votes in the Washington primary than he did in the Washington caucus. Obviously Clinton got more popular votes in the primary than she did in the caucus there also - but factored in sheer raw numbers Obama defeated her by far higher popular vote numbers in the primary than in the caucus - in the same state. Though his ultimate winning percentage may have differed, either higher or lower, had the states that Bernie won in caucuses held primaries instead, there is no plausible reason to believe that the outcomes would have been different - Sanders has been winning those states in massive blow outs. Had they been primaries instead Sanders raw popular vote victory margins in them would have been much higher.
Second, the actual math. We are about mid way though the nominating contests, and the first half of the schedule strongly favored Clinton with its emphasis on Southern states voting early. In 2008 Hillary Clinton picked up over a million more popular votes than Obama won in the states that will be voting this year on April 19th and the following week alone. And no, one can not simply assume she will have an advantage in those states this year also. If one were to predict Clinton's 2016 results based on 2008 outcomes, she would be the one well behind in popular votes now based on Obama's 2008 performance in Southern states. Every election cycle is unique.
And of course the overall popular vote count doesn't include Wisconsin either, or a slew of other upcoming states including, for instance, California and Oregon. In 2008 Hillary won California - our most populous state. This year I believe it will be Bernie piling up the votes there instead.