Despite your insistence on the degree of fame this person carries, i've no idea who she is.
And i find such claims silly and pointless. Taking something such as a music video, particularly from someone in the mainstream, means little in terms of claiming to know much about them. Often times much about a performer that you see is not much more than a character. And the bigger the celebrity, especially in music, it also usually means the more control the record company has over the artist. Many artists have been known to be forced into changes due to the contracts they signed. Vanilla Ice, for example (and going way back) was not some giant pant wearing buffoon he was presented as, and did not care for the image he was portrayed as. But he was contractually obligated to do what his record company told him. And that goofy image is what they presented, as a way to counter MC Hammer's fame.
So it's never easy to know where an artists choices end and the record companies begins.
Not to mention what is the good in worrying about whether a celeb is (supposedly, based off of loose, circumstantial evidence) a satanist or not? There are plenty of artists in varying genres that plainly express a varying type of beliefs, especially in music.
So i see nothing of value or use chasing around after celebrities, dissecting their corporate made videos, so as to accuse them of certain beliefs. Whether a 'devil worshipper' (which is actually a rare belief), atheist, agnostic, polytheist, monotheist, new age or worship the flying spaghetti monster, who cares? If they're a non-Christian isn't that singularly the most important designation? Aren't they all doomed to the same fate no matter which of these labels they fall under?
Aren't you better off praying for them, rather than spreading rumors about them? Drawing attention to them. Encouraging more hits on their videos? They say the greatest trick the devil ever pulled was convincing the world he didn't exist. That may be true for the secular world. But for Christians the greatest trick would be to have them chase him around, distracting from the true purpose God calls them to. How effective of a witness are you worrying about what a celeb believes? And accusing them of things from such a distance?