How might Mackenzie be a fake?
I believe she's a good (but not elite dancer), and I think that's what her public reputation is (a good dancer, but not an elite one), and about what she tries to represent. The last two times she's gone to Jump, she's finished 3rd and 3rd.
She's done better at the show's competitions, so maybe the producers and editors are exaggerating her talent to some degree, in what they produce and show... but I don't think they're exaggerating tremendously, into acting like she is a rare elite dancer. And besides, what the editors do isn't really in her control.
So I'd say she's not fake in pretending to be a far better dancer than she actually is.
I think her reputation as a singer is that of being good compared to average... but not a reputation as an extraordinary talent. I believe that's also about what she tries to represent. And I think that's about where her ability and training lies as a singer - good, but not exceptional. So I don't see her as a fake as a vocalist.
She doesn't have a reputation as a saint, who never does anything wrong; and I don't see her trying to pretend that she should be considered a perfect saint. So it's another area where, to me at least, she does not seem to be a fake.