Hillary has stopped playing games with Sanders. She's frustrated at the fact that Sanders' numbers aren't falling off even though he lacks a path to victory. Further, she wants him and his supporters to know that he won't be the nominee, and that they better get on board.
I'm, frankly, fine with her new tone. Being gentle with Sanders and his supporters has only emboldened them to push back against her candidacy. It's time to force them to confront reality.
The reality that they won't be voting for her, because rather than make any attempt to reach out, negotiate, or otherwise act like a politician, she's instead demanding to be crowned?
She already said that she wants to sit down and negotiate with Sanders on the platform.