Filmed in a dark club, yet still high quality like that... we're not talking about one stealth flip or a mini cam corder hidden from view. There is probably a guy with a professional shoulder mounted camera, another mic guy with a boom, a light guy. Possibly other cameras. A set, with wires everywhere.
If it were a real bachelorette party they would be spooked by the camera and would be hiding or staying out of view. And certainly wouldn't act like that because the filming would be obvious.
It's cool that they make it look fly-on-the wall, but you have to stop and remember that there's a film crew on the other side of the camera.
This is staged, it's exciting or entertaining for some to see others go down the wrong road. That's why they make these films- they sell.
There's a site called dancingbear that specializes in this bachelorette-gone-to-the-dark-side thing. The films above may be from there hosted on another site for advertising.