Also remember Hillary and the party have been treating Sanders with kid gloves so far. In 2008, Hillary didn't really go ham against Obama until after Super Tuesday when she still hadn't put him away. This time she has the black community and the party on her side whereas before the black community was on Obama's side as well as a large chunk of the party (Harry Reid, Ted Kennedy, etc.)
It's all just the preseason for Clinton so far. She's doing cheap stuff that can't really hurt her, like identity politics games and criticizing him and his supporters for their negative campaigning. Iowa was supposed to be a toss-up. NH was supposed to be heavy Bernie. What we're expecting next is a string of victories in Nevada, South Carolina, and the Super Tuesday states that should shut Sanders' campaign down for good. If that doesn't happen, then we'll start with the real attacks, like investigations into Sanders' communist and other far-left connections, his checkered past (especially as a radical revolutionary in the 60s and 70s), any controversies from his tenure as mayor of Burlington, etc.
The Clintons know how to play dirty. Hillary fought tooth and nail to win the 2008 election, she hasn't come this far to not go twice as hard in 2016. The fact that she's still barely even trying is in and of itself a reason to think she's still confident. Case in point,
she's going to start focusing on a Black Lives Matter agenda and campaigning with Trayvon Martin and Eric Garner's families. This should help her against Sanders, but it also helps her in 2016. She's not burning bridges to kill Sanders here.
In fact, Clinton would probably be perfectly content to keep Sanders alive and beat him 60-40 in most of the remaining states. When the Sanders squad on campus furiously rushes to register every single college student and push them to go vote for Sanders, they're also registering Hillary voters for the general election. Assuming Hillary doesn't lose and Sanders doesn't leave a permanent wound as he goes down (virtually impossible with Hillary considering all she's been through), Sanders' continuing presence in the race is a positive for her.