Fame is awesome for those who are in the entertainment industry because the attention celebrities get says a lot about their popularity and how there are more supporters than haters out there. However, it is because of fame that makes them the easiest people to target since words will spread out faster and further.
I doubt that it is her in the video because she does not seem like the type of person who will go that far for attention. One can say that everyone has hidden sides to them, which is true, but if she was planning to go into the entertainment industry, I doubt that she will do that. There are so many of these video controversies floating around, and most of them turn out to false. For all we know, the video is not even old. An anti-fan could have done it to ruin her reputation.
Either way, I still support Jiyeon. I will be disappointed if it is true though.