There was nothing out of norm about it. Worse would have been for her to do what Gore did. The election results were razor thin. If anything she had every right to wait for recounts. She did not. She conceded.
Gore took a general righteous approach, in my opinion, but lost (not interested in re-litigating that). Hillary had no path to win by midnight, had nothing so close as to make recounting necessary. She was just... well, she probably felt totally blindsided by the loss. And then delayed her concession unnecessarily. It's ok to acknowledge this. It wasn't a real problem, just violating norms.
Again, we can point that without diminishing the insane damage the current President is doing to our democracy.