Unless she falters early on, or unless another Democrat catches fire and emerges as the alternative before the early primaries are over, I expect her to win.
But keep in mind that is exactly what happened in '04. I remember laughing at Kerry's campaign when he had to loan himself money, saying something like "he may not be toast, but the bread's gettin' warm." But what propelled him back into contention and the nomination was the perception that Howard couldn't win. It was helped along by the scream (Yeeeaaaggghhh!!), but the momentum was already there.
That's true, but there is one major difference between Dean and Hillary. Dean was an outsider candidate that the party machine never really wanted a part of. His early success was a house of cards built on internet donations and support from people who usually don't vote. That's why he underachieved early and imploded so dramatically at the slightest misstep. Hillary has a much stronger fundamental base of support with the core of the party that it will take something dramatic to knock out those underpinnings.