While I tire of the media treating Democratic primaries and caucuses as winner-take-all events when the race is really for delegates, which are awarded proportionally, yes, she did have a big night. Her campaign set the goal a few weeks back that she had to win both Texas and Ohio, and she's apparently done that.
How did she do it? So many factors. Perhaps it was the "3AM" ad that her campaign's been running, sowing distrust in Obama's leadership. Perhaps it was Obama's mess up on NAFTA. Perhaps it was the sympathy evoked by the media dogpiling on her, which SNL picked up on nicely. It'll take some time to sort this all out, and it's really hard to say at this point whether it was her efforts that did it.
We should remember, though, that this is far from over. It's hard to believe it, but this thing is going on at least until the early summer. The Pennsylvania race will be intense but it won't resolve anything. Also, the odds are still long against Clinton winning the nomination. She just doesn't have the delegates, unless a lot of superdelegates are willing to vote for her even when the bulk of regular delegates are leaning Obama. She has to decide how negative she's willing to go on the guy who still is the likely nominee.