This is the Worst and Most Hilarious Twerk Fail Ever. We Promise You.
That said, and hilarious WHOOPSIE DAISY aside, who the fuck would want their girlfriend to send them a video like this? I don't know, maybe it's just me but I think I'd rather her just come over and grind on my penis instead of making a dumb fucking video in her spare time. But I'm old fashioned like that.
Warning: Watch it with the volume down. She screams, LOUDLY, when her leg catches on fire.