Fake but funny.
I first noticed that there was no "passenger restraint system". the rider would have bounced all around in there.
Then, as the comments at the video site note, it was not the same woman coming out as went in.
Britney got paid to walk in and sit down. Someone else took the ride....which probably was only an empty out house bouncing up and down.
Actually, I don't know enough about how Britney looks to know she was the one going in.