They Should've asked your permission before they traced your art, you should try talking to them about it civilly. However if that doesn't work you could report them or get your followers to harass them. (Which I don't recommend)
I dunno, I feel like messaging them will embarrass them or upset them, and they’re prolly a kid? In the long run i dont think its worth hurting feelings, since them tracing really doesn’t hurt me personally, but I might hurt them unintentionally.
And I would never, ever sick my followers on anybody intentionally. That’s just irresponsible and shitty.