Not being a TV watcher, I had never heard that cackle before, though I had heard about it here.
Even without context, you can tell it's fake - it comes from the throat, whereas a real laugh comes from somewhere deeper.
I suppose it's been calculated (by somebody) to make her appear human.
"The secret of success is sincerity. Once you can fake that you've got it made."
---Jean Giraudoux
Read my tagline.
Next time you do get to see video of Hillary "laughing," be sure to watch her eyes. The eyes always give a fake laugh away, the same way the adam's apple always gave "Janet" Reno away.