I suggest you watch this video without sound. There are a few main giveaways that show that this is fake. It's easier to see through everything by just watching the body language.
This was a great tip! Thanks for that. I missed a couple of the observations you mentioned and realised I may have been the one who was pranked in the end. I can't say that I was vetting the video though. I just took it at face value. There are things you mentioned that I agreed with, but also some things that were to extensive for my knowledge.
When the camera cuts back to the faces after grabbing the butt you can see that their lips hadn't been locked. She never goes under his underwear, which he is clearly wearing.
On the kissing part, when he grabs her butt, her hands just drop and remain there. She didn't seem to be that into the kissing. This is shown around 2:48 of the video. I can't place this as strong clue, but it was something I picked up.
Also, she used her right hand to jerk the guy off, but towards the end of the video she is cleaning both hands off the side of her pants. She placed more emphasis on cleaning her left hand as well. This was also a clue I picked up.
The other tangential conclusion is that this video must have had multiple takes, most likely because she wasn't being serious or acting poorly.
Yeah, this is something I also didn't pick up. The multiple cuts from different angles does suggest that the scene was played out more than once. They may have had two or more camera-men, but I believe it was more the former.
I can't put strong weight on the clues I picked up, because I picked them up with the intention of finding what may have caused the video to be scripted. However, I do agree that the video is scripted. Thanks for pointing it out Slim. I certainly learnt something, and will definitely be more observatory when I watch videos.