However, if this video is your production, or your have the copyright owner's permission to re-edit the video, you should have access to an HD or 4K version of the video or even the original video elements that were used to edit the video. That will give you a better chance to work on it.
+1 @Musicvid ... how does one rotoscope the opening shot with the singer flaying her arms about in 480p and with any hope of tracking those dodgy edges - even in Mocha Pro. It wouldn't seem that the OP has access to the original footage which suggests ....
Unfortunately, I don't have access to a better quality than the youtube video. But it would be ok if the edges aren't clean, I'm not looking for a clean thing that would give the illusion that the background wasn't removed.
I fully understand that. But have a look on YT at the original YT upload - it's a murky 480p video and it will be very hard to find a good edge on the flaying arms of the dancer to set a good mask around. Like I said earlier, the OP needs to get the original HD/4K footage to do this well.