I guess I don't understand.
There's millions of YT videos of amateurs singing copyrighted songs, or even signing them, or playing the song on an instrument like a guitar. What was so different about Ally's videos that YT shut down her account? I mean, I did a search for Living on a Prayer (Bon Jovi) and it came back with 8,840 videos. And only a small fraction of those are actually Bon Jovi singing them. So are the remaining all in violation?