She's gonna be scared of happy AND her fans after this...
Ch-ch-check out fan video of the decidedly not dope attack (below)!!!
[Image via Fifth Harmony/Instagram.]
Pretty sneaky, sis!
The sibling rivalry came to a head when in order to take down Derek's hot take on Macklemore's Can't Hold Us, she totally pulled out a secret weapon — the real Meghan Trainor came out to help her sync All About That Bass!
But then things really heat up when Derek plays both Sia AND Maddie Ziegler with an interpretive Chandelier dance while Julianne Just Had Sex onstage!
[Image via Spike.]